Consider a monopod that you can also use as a walking stick.
Since you still have time, rent a 500 mirror lens to see if that is what you want. I bought a 500mm Tamron for a trip to Alaska (big spaces) and found that, except for a few bears, it was more lens than I needed. It was too much lens for Denali even at 35 miles away. I have a Canon 70D and carry a 28-105mm and a 70-300mm. No matter what I carry (I have several other lenses) I find that I use these two 95% of the time.
I suggest you take a day trip, pretend you are on your safari, and see what you use. I live on the New Jersey coast and use the beach for long distance tests. If you discover in Africa, that you should have brought.......too late.

Your first photo is Devil's Club. If you grab the stem, you will know why. Biggest thorns I have seen. However, the locals use the plant in a cream that relieves pain. Check Silverbear Sundries (http://www.silverbearsundries.com/index.html)

If you are looking for an inexpensive upgrade, look for a refurbished Canon 3Ti. They are hard to to find but perhaps one of the best & most popular because it has some bells and whistles, but takes excellent photos. The newer Canons have a few improvements but many seem to be for the video function. You can also get refurbished lenses from Canon, (full warranty) or excellent used from KEH or MBP.
A word of caution in Iceland- ask for English menus in restaurants. They have a few unusual "delicacies" like fermented shark or whale testicle beer. If you trust the waiter to recommend the house specialty, ............

I have a Lowepro Sling bag. (http://www.lowepro.com/camera-sling-bags) and have been very happy with it. I can move it out of the way to rest on my back when shooting and pull it to the front for changes. It has 3 external pouches I use for lens tissue, snacks & water, and an adjustable internal padding system. I can carry a Canon 70D, 4 lenses, flash, filters, spare batteries & SD cards, plus assorted cables.Look at the Lowepro site to make a choice but best prices are from B&H.

Both visually appealing. Great shots. I think #1 improve if the red flower were at one of the rule of 1/3 points instead of hiding in the corner.

Please forgive my ignorance because I only own 1 "L" lens, but are they not standard diameters for various filters? ND & CPL would be expensive if they required none-standard threads. What does a $640 hood do that a $36 hood doesn't? On the Canon site, both hoods read: "Designed to prevent stray light from entering the lens in order to keep unwanted glare from affecting your photographs.
Compatible with the EF 100-400mm f/4.5-5.6L IS USM lens"

[I love critiques- I love to get them, I love to give them. I love to watch them but I ain't gonna do much of this here on the HOG- well- at least in this section. I mean, this place is a MINEFIELD of hateful arguments, cussing, name calling and verbal combat over things impersonal things like a skylight filter, different styles of photography, a flash unit or a lens.]

I shortened the original post because it did get long, although I read it all. I was a science teacher for 28 years, and taught in the education program of a university. If you are going to be effective, you cannot browbeat the student. Once they turn off, they hear nothing, they learn nothing. To paraphrase a movie, "If you can't say anything constructive, don't say anything at all".
I am neither professional (although I did several years on weddings) nor an amateur. I have been shooting for 50 years. Sold my first photo 45 years ago. I can learn from people better than me, and also from people with less experience. Sometimes they ask why there are certain rules, and I just assumed that those rules should not be ignored. When teaching prospective teachers, the only acceptable critique is " I think you might want to try.......(whatever)" If they don't listen to you and internalize it, and make it their own thought, they will not use it. I have to give ideas that they think might be useful or they will be ignored. Those who flame a poster are not remembered next time the photographer is in the field (studio) If you want to be helpful, your critique must be useful. You must listen to what they are really asking. If they are asking about composition, comments on exposure are not useful. Critiques are supposed to teach. You cannot teach a closed mind. People post because they want to learn: so teach ideas, offer something to try. It is an art. Your way might not work for them, but if you try to be helpful, maybe they can use part of what you suggest to achieve their goal. Beginners and experts post questions & photos looking for ideas. When you post a reply, before you hit "send", ask yourself if you were the recipient, does the reply seem helpful? If not, don't send it.

Depending on time, consider buying either from KEH.com or from Canon.com refurbished. Direct from Canon will cost less than new, and comes with a full 1 year warranty. KEH is used, but their "like new" or "E+" are hard to tell from new. Canon refurbished is not used, but may have been in a store. It is 100% inspected. I have been happy buying this way.

As a buyer, I would still need a Certificate of Authenticity. But then again, is it the picture that is important or the artist? I would pay more for any Ansel Adams print than I would for my best work. But I need to know it is authentic.

1/50 does not make it an original, just the first of a series, which still adds value. The term print vs original does not have the same meaning in photography. The question you need to answer is whether the photo is unique or one of a series. If it is hand-signed, without a number, it "could" be the original, or first copy. If I were to purchase a piece of art, there are several things I am looking for. Generally, all prints are "signed and numbered" as part of the duplication process, no matter what the mechanism. Those from the artist are "Oversigned" Below the number, it is hand signed. The 2nd thing I want is a certificate of authenticity. This will tell secondary market purchasers if I have one produced by the artist, one of a series of commercial prints, or a unique one of a kind. You cannot tell that from the print. Some of the oversigned prints are just initials, so if you don't like your signature, develop something unique that can be identified by dealers. If you expect your work to increase in value or be sought by collectors, you will need to think of this now. Otherwise, your signature is just used to protect a copywrite. BTW, you should look up photo copywrite threads on this site. There is an extensive discussion on that issue.

Wrong kind of cloud for rotation like a tornado. Little in nature is this perfect as a circle. If I had to guess, I would say an artifact caused by the window and/or the lens.

I agree on so many issues here. Most of Congress, both Dems & GOP, have no idea what the average person has to do just to get by. While they all "support our military", they v**e to cut the funds that families need. Housing, Commissary, medical, all used to support the family. However, if a soldier is deployed, very often the family ends up on welfare to get by. This is wrong. The GOP argued for years that health care should be available across state lines. They now have an absolute majority, and can't get this simple thing done without complicating it with tax cuts for the rich, who don't need it. Instead of one, big, complicated bill, fix all the little problems. ACA is not failing. It is being sabotaged by those who didn't like the idea that Obama got it passed when the idea was originally a conservative one. (Heritage Foundation plan- first used in MA by Romney) Remember, Obamacare was a label adopted by the GOP. So many people want Obamacare gone, just don't touch their ACA.
Perhaps term limits is the answer. You get a total of 12 years in Federal elected service, or 15 years combined state plus federal elected positions, and you are not eligible to run again. Period! We need elected officials who are representing the people of their district rather than the party or their own re-e******n. Jefferson said it well. Service is not a career, it is an honor. You serve your term, then go home and earn a living under the laws you wrote

I would suggest you look into renting a lens for the event. You can decide which is best. If your store rents with an option to buy, consider that.

Ask them what they like, what kind of pictures interest them. There is no point in trying to teach them something they don't want to learn. Go through pictures of travel, art, people, wildlife; there are plenty on line. Have them show you pictures they took that they like but wish were better, then give an assignment to make a better picture. Single assignment. When you have discussed that one and they are happy, move on. Make suggestions, like macro, still life, but not flowers. Colored glass bottles, and play with light; same picture but different lighting. Sports picture, getting a single player that tells a story. But if it isn't something they are interested in, they will not pay attention, and they will not retain it.

Too many of the photos on google or other sites are enhanced snapshots. Try low angle, high angle, or look for detail shots that show unique features. There are landscape shots and there are art shots in every scene. I have been trying landscape with a moderate wide angle, but from the ground. I carry a yoga mat to I can lie flat and not get dirty, or lie on my back and shoot up.The question is if you can find a viewpoint that has not been done. Go artistic instead of event recorder. Is there anything unique about the light? Instead of posing people, can you record them doing ordinary things? Photograph life instead of just pictures