Buy it with the 2 lens kit.
Light, compact affordable and covers most all the focal lengths from 18mm to 210mm.
Then use that great little camera to have a wonderful trip.

Most 100+ year old photos are odd sizes like 3.5x5.25 or something similar.
I have hundreds of odd size 100+ year old negs.
None solar fit the 120 format unfortunately.

Remember the op has over 100 year old negs it appears. Likely they are not 35mm.
Newer ones perhaps but older not likely. Should use film area guide with these negs or if a flat glass panel was provided use that for negs if the guide is too small.

No such place as Columbia, SA. common error by Americans.
The Andes is pretty broad as there is a large part of Colombia in the Andes.
Having lived all over the country for many years and not knowing anything more than Andes I believe your choices of lenses will be absolutely excellent. Dump the 50mm unless you are totally enamored with it.
The 10-18mm will be great for villages and cities where spaces can be quite tight. The 18-400mm will be a great choice for your all the time on the camera lens and allow for fast reaction to amazing things happening there.
If there is space for the 150-600mm then by all means bring it along and leave the 1.4X converter home unless again you have space and really want to bring it. Tripod will be good if there is time and easily carried and totally out of your way as you walk, if you are walking.
Your son will be a great source of where to go and where not to due to anti government forces in control.
Colombia is amazingly diverse and beautiful and sounds like you are going about it the right way by an actual resident and not some canned tour. The campesino busses will be amazing and take you most anywhere you will want to go in cluding trains if desired.
Enjoy and have fun.

You were not PC enough and perhaps actually told the truth about an issue.
That is an immediate grounds for being banned.

Find attached the scanned negative straight from the scanner to my computer.
Note I scanned an area larger than the negative because of the odd size I will now crop/straighten if needed. Adjust light/dark contrast and clarity as I perceive as needed and even flip as I will this one.
You can decide on your negs to best suit you, I will not pretend to say what you like or should do to adjust.

Here are a couple of scanned negatives showing what I was talking about adding text to them.
There was a period of time these could have been made but I was guessing by age appearance and from journals.

I am currently doing the same thing with the Epson V750. I have found that the negatives produce much better scans. All of the negatives from the early 1900s and earlier are odd sizes and I use the supplied glass platten to hold them. Most are large enough so only 2 fit at a time and others 4-6 at a time.
They scan directly as positive images directly to the computer in the proper folder and then exposures adjusted in PSE.
I would only scan prints as a last resort.
Once in PSE rotate and crop as needed then use the crop tool to add a white space below the image and write who, what, where and when along with brief comments if detail clarifying the photo.
Then save it.
This is best for me as when shared with anyone of any technical ability can immediately see the who, what, where and when etc. Just by reading beneath the photo.
My family love it and if there is an error of any kind can immediately notify me and I make the change in PSE immediately and resubmit.
Any other questions let me know.

I am guessing that you try and not use your shutter release either as it will likely wear out along with your on and off switch..

Perhaps all your DSLRs sprayed oil but none of mine ever did.
Show a technical paper stating ALL DSLRs spray oil.

Interesting as I NEVER had a mirror throw ANY oil or dust on my sensors.
And yes if it did I would have quickly noticed.
On occasion after a beach day and changing lenses I would get something on the sensor but easily cleaned it off my self. But outside of those 3 times it never got messed up.
Was there something wrong with your camera? I never heard of people before making a complaint of this issue here or elsewhere.

Closing the shutter when off does nothing to shutter count.
All your DSLRs do this if you look. And you never worried about it.
Different models of mirrorless close when off, very few, most stay open.
All depends on the maker's design decisions.
So get the camera you want and don't worry just be smart if changing lenses.