What is the longest stretch of boondocking do you plan on doing at a time? 4 days? A week? Longer? How long will the established campground stays be?
How far out from civilization do you plan on going? 1 hour? 4 hours? Longer?
With a good mix and not too far out, you can get into an area, stay close or in the town for a couple days and locate emergency vets, etc., then head out to boondock - you'll know exactly where to go if the cat has an emergency while you're boondocked.
But, no matter what advice folks can offer on how to do it, the question YOU need to answer is:
If something happens to my cat during this trip will I be OK with that?
There is no right answer - but the answer you choose will tell you what you should do (no matter how hard that decision might be).