Hopefully you're going to stop for the night somewhere - that's too long for the cats to be cooped up without being able to go to the bathroom, and taking them potty at at rest stop probably isn't a viable option, they won't "go" on command like a dog will. Also, that's a really long time for 2 cats to be in a single kennel. Can you borrow a second kennel so each cat will have their own, then there would also be room for a small catbox in each one. Good luck, you're braver than I am!! Another thing to consider - are they used to car rides? Some cats get so stressed they get sick and start barfing - my cat does this, then the other end starts going - not a pleasant experience for any of us!