Travel advice for two kitties

I will be moving my two kitties and myself soon. Not so bad from a human perspective, but these kitties only go outdoors/for car rides when they go to the vet, and my oldest is 22 (not a typo) with kidney failure, so she drinks often and a lot. Does anyone have any sage advice that just might help make this trip less stressful--for all of us?

Planning on moving from South Carolina back home to California. I purchased a car out here so we've decided to drive it back. Of course, boyfriend wants to bring his cat (who is somewhere between 7-9 years old), and of course I agreed. Much rather take him along than let him stay here (his mom has 14 dogs, etc.). This presents a huge list of firsts for me: First road trip across the country, first road trip I'll be driving, first road trip with any kind of animal and the list goes on. We're not leaving until the second week of September, so we have a long time to prepare for this trip.

So far the plan is to start the cat off in the morning with a walk and watering and to do the bulk of our feeding at night in the hotel. I'm thinking of stopping every 2 1/2 to 3 hours for breaks which would include more water and walking. I have a list of things we need to buy prior to the trip: Collar, harness, leash, tag, kennel, bowls, blankets for the kennel, dog first aid kit, small bag of his food. On top of that I need to get him up-to-date on his shots and somehow manage to find paperwork of his neuter for licensing in California.

Also, in addition to road trip advice, I really would love some advice about how to go about introducing this cat to my dog when we get there. Both are male and neutered. I know my dog gets along with other cats fairly well; but, I know that the only reason his cat was ever neutered was because he was fighting with another non-neutered male. My only thought was to get them away from the house to do introductions and crate them separately at the house until we're comfortable with their behavior.