If your dogs get a bit stressed by long car rides, you may ant to consider some calming chews from a pet store. But you list looks pretty complete to me... besides perhaps treats to do some training and tricks, and to reinforce good behavior.
Are there going to be any times where you might be hanging out with them in the car for a while? Eating lunch at a rest stop or taking an hour or two's break? If so, and if the weather has any chance of being warm you might want to look for a battery-powered fan to help keep them cool while the car is off. There's some that attach to crates, and I know some dog sports people swear by the Ryobi fans because you buy the batteries separately and can charge up two or three to swap out if needed - that's probably on the pricier side though! I'm sure there's other decent ones out there.
We also like keeping wet wipes and/or paper towels for small messes (or to get treat residue and dog slobber off our own hands) when we're driving to and from the in-laws with our boys. It's only a couple hours - haven't done a proper road trip with them - but we'll sometimes stop for a walk or run on the way, and it's nice to have a quick cleanup kit without breaking out the towels and dry shampoo.
We are using seat belts in the car. And their crates are wire so they get good ventilation. I'm also taking their tie out equipment. That was a last minute inclusion. I'll look into the calming aids. I'll definitely remember to pack paper towels. Thank you both for the great suggestions.
My Dad decided that his dog Zep is going to stay with a friend of his with a 6 foot privacy fence. He's a fence jumper when he can't see my Dad so I'm hoping he won't climb this one and trying jumping out. I'd prefer to just take them both. Finnlee is going with me on the trip. I found out yesterday that my vet didn't give Finnlee his Distemper/Parvo booster so I took care of that this afternoon. Finnlee is all current on his vaccinations. Zep got all his at the first appointment. I'm going to make copies of their records. I'll give copies of Zep's records to the friend where he's staying and taking Finnlee's with me.