Buckets might be the way to go, with the pool-noodle idea as a seat "cushion". I have buckets in 3 sizes; 5, 2-1/2, and 1 gal. This is a little 1 gal. bucket I use around the pond. I don't know, maybe too small, but with that size I could get away with more discreet disposal, carrying it to & from the latrine every AM, LOL! This was the size I could also use as a shower caddy [a different bucket for each purpose, though....of course]. Either that size or the 2-1/2 gal size might work. We're driving [camp's a good 12 hour drive from here -- in west Texas] and carpooling with about 30 scouts & adults. Packing space will be at a premium, but then, buckets are good for carrying stuff in when you pack (remind me to pack a can of disinfectant....).
So, maybe I need to bring a couple of buckets inside for a few nights and give them a try-out.....?