I hope this isn’t too late to be of use.
I totally agree with LV that the cats should be in their carriers at all times. I know there will be a temptation to stop and let them out for rest breaks but every time the cats are out of their carriers you run the risk that they will somehow escape—and in strange territory, your chance of recapturing them is pretty small. I imagine it will be a long, one-day trip. For that reason, I would not bother with trying to feed or potty them enroute. You might put small bowls of water (about half-full to avoid slopping) in their carriers but in my experience, cats are usually so stressed out by travelling that they pretty much shut down for the duration—no eating and if they can “hold it” until they get to their final destination, they will. I always carry one of those disposable turkey-roasters and some kitty litter when we travel with the cats but I have never had a cat use this travel litterbox enroute. I would also feed them very lightly, if at all, the day before you set out. Fasting for a day won’t hurt them, though I would make sure they had a chance to drink water. When you get to your new home, it might be easier to confine them to one room for the first 24-48 hours, to give them a chance to relax and regroup before giving them a new house to explore.
Good luck!