17-55 f2.8 the 24 - 70 isn't wide enough on a crop sensor

I have a Macbook pro with two (3T) external HDs. One for Photo storage and a second to back up everything. Lightroom recognizes both external HDs. All you have to do is plug in the HD, set up the filing system you want to use on that HD within LR and drag and drop folders full of images into the appropriate folder. Your main catalog (and hopefully only) catalog will recognize all of the images on the external HD. If the external HD is not connected, you will see question marks but the file system will be visible. I keep images that are somewhat current on the internal HD and older images (over 1 year) on the external HD.
This is really simple and don't let some old LR unbeliever tell you differently.
I would be happy to walk you through the process.

I have the older version 24-70 2.8 which is a great lens but big and heavy. The new VR is even bigger and heavier with a larger filter size which could add $200 easily . More money and more weight, you really must need the VR to upgrade. Frankly, I never felt the need for VR in that range but certainly appreciate it in the 70-200.

I print my own fine art prints for sale and show on various fine art papers, usually Epson Velvet Fine Art or Hot Press Bright.i find that I can "fine tune" the final print which is not possible unless you are working with a truly custom printer. I do not print borderless but leave at least 1" of paper surrounding the image. I sign with a 6B Artist pencil on the border of the paper just below the image on the right side. The mat is cut to expose 3/8 - 1/2 inch of the unprinted paper around the image and the signature. This is common in the water color art world and among fine art photographers and allows the viewer to appreciate the quality of the paper. Also, if the mat is signed and the purchaser has the image re-matted, the signature is lost. If you are using glossy or semi-gloss, the pencil doesn't work and in my experience the artist does sign with a sharpie.

Thom Hogan publishes the best Nikon guides with complete, easily read descriptions of every aspect of the camera and how you should think about and utilize them. I have had his D200, D300 and now D800 books. Check out this link.
http://www.dslrbodies.com/books/bythom-complete-guides-/nikon-d500-guide.html

That is true but that doesn't work if I am shooting a moving subject and I want the exposure to change with the movement as I normally would.

On my last I meant my "now free thumb" - sorry.

I shoot a Nikon D800 and find the benefit of BBF is to be able to shift between single servo and continuous by either 1.) composing, establish focus on the desired subject, release the BBF button to hold focus and recompose or 2.) when shooting continuous simply holding the BBF and shoot. The The first instance is usually when I need to hold exposure and recompose. Therefore, after establishing focus and releasing the BBF, I hold the AE lock button with my now free index finger.

I was fortunate to be able to shoot D1 Lacrosse for four years with many published shots and was able to discuss shooting strategy with a number of pros that I met. Like you, I have a D300 and D800. Here is how I would look at the problem. The goal is to catch peak action and isolate it from the background with a tack sharp image. Therefore, frame rate and max arperture are important considerations in addition to shutter speed. I would put either the 70-200 or the 200-500 on the D300 (try both) so you can get the higher frame rate and set it on arperture priority wide open. The D300 resolution will be more than adequate for substantial cropping or enlargements. Some of mine went to poster size in the locker room. Set the ISO so that you get an absolute minimum 1/500 but 1/1000+ is better. For most conditions Nikon auto white balance works well but I would check it under the lights. I only had issues when shooting other sports in an arena. You can probably hand hold the 70-200 but would definitely need a monopod for the 200-500. Shoot in bursts of 3-5+ shots to catch peak action and improve in-focus percentage. Practice your panning. Put a 24-70 on the D810 and use it for sideline photos or pregame shots of the coaches and players interacting. As to jpeg vs. RAW, I usually shot in JPEG, remember they are sports photos not fine art or portraits and you will want to minimize the post process work. I would usually shoot 400-600 frames and would deliver 20-30 to the university and parents. Chimp, check exposure and delete as much as possible between plays or during time outs. The other question is do you move up and down the sidelines or generally stay in one general area. Try both by alternating between quarters. Since football generally moves in one direction, I would tend to move up and down the sidelines where possible while not disturbing players or coaches who couldn't care less if you get a great shot. There are usually rules for photographers so ask other sideline photographers or the person that hands out the sideline pass. Study rosters ahead of time and make a list of the players numbers of whom you must have. Good luck and have fun. The game is much more interesting from the sidelines.

I have never had to recover from a crash but following is my backup strategy. I import photos to a folder in Lightroom on my laptop Hard Drive.. After I have completed my workflow and feel I no longer require immediate access to certain folders when traveling (likely once or twice a year) I move them to an external three terabyte hard drive within Lightroom. I have a second 3 T HD that backs up my entire system, laptop HD and external HD. That way I don't have to worry about what to backup because everything is automatically backed up. In case the house goes up in flames the whole system is backed up each night by a cloud based system (Code 42, Crash Plan). When traveling I carry a portable external HD for temporary backup. Periodically, I check the backup drive to confirm the system is still working properly and get weekly backup reports from the cloud based system.

I did this trip last year. Don't miss Dead Horse Point State Park https://stateparks.utah.gov/parks/dead-horse/ . I was as good as any of the National Parks.

I used an Epson 2880 for about 5 years and in the end the fine art feed process was difficult at best but still great prints. I upgraded to an Epson P800 last year and it works flawlessly. I print on 17X22, 13X19 and 8.5 X 11 Hot press, cold press and velvet fine art and never a misfeed. Same great color and resolution. Knock on wood!

Seems like we are making this way to complicated. In the Development Module go to File, Export. Go to Image sizing and check Resize to Fit. Then select Width and Height (two boxes will open), or Long Edge or Short Edge as necessary (one box opens) and type in the desired dimensions.

I sell signed, unframed, unmatted prints on fine art paper 12 X 18 for $200 and 14 X 21 for $300.

Call Nikon service: 1-800-NIKONUS, and send it to Nikon ASAP!