Sounds like you have a solid plan and I feel like a lot of people here have a tendency to go overboard with moving animals.

The first thing to do is to stop feeding 2 weeks prior to moving, or at least this is what I did. My snakes have been driven from Leavenworth, Kansas, to Colorado Springs, and back. On the way to CO I put them all into 1 large tub and put it in the back seat of my truck, as it was an 8 hour drive and they were going straight into the house when I got to CO. From KS to CO they stayed in their tanks and went straight inside when they got to the house. Balls live, and brace yourself, OUTSIDE in Africa! Are there temperature swings out there? Yes. Do they always have a warm basking spot that is at 92 degrees? Heck no! While they can self regulate their temps outside, there will still be times where they can't get as warm as they'd like, and if they couldn't handle a few hours without perfect conditions they would die in captivity a LOT more often. If your snakes don't have a heat source for 24 hours and the temps don't drop below 75, then you will be absolutely fine. Even a drop below 75 would be fine if it were only for a short time.

As for your question about taking them inside when you stop at night - definitely. The car should get pretty cool at night, which would put undue stress on your snakes. Good luck with everything and let us know how it goes.

Side question - I'm concerned that your Dumerils is only 2' at two years of age? Is he a poor eater?