S.G.
We did two moves, from Virginia to San Diego and back, with our two cats. It wasn't too bad.
1. get two cat carriers. Insert cats.
2. Every time you stop for gas or to stretch your legs, let the cats out of the carriers so they can eat, drink, and use the litter box. For a twelve hour trip, I would just get their regular box and put in fresh litter, scoop as needed.
3. They'll probably yowl and protest initially, then settle down for a looong nap. They are cats, after all.
4. When you get to your new destination, let them explore on their own and don't be surprised to find them huddled up in some unusual spots while they get used to it. When we moved, we found one cat huddled behind the toilet and the next one crammed up next to the fridge. I think they liked the enclosed feeling. So maybe leave their carriers out, with the doors open, so they can run in there to feel safe.
It won't be as bad as you think.