There are a lot here that I enjoyed with my sons. One that hasn't been mentioned is Shiloh by Phyllis Reynolds Naylor. We listened to a version read by Michael Moriarty. My sons are in college and grad school now and I can still remember how quiet the car was when we read that book. If you and your kids are dog lovers, it will be especially moving. Have a good trip, OP!

Dragon Teeth by Michael Crichton. Based on the true story of the competition between pioneering paleontologists at Harvard and Yale. Is better than it sounds.

Good Omens by Terry Pratchett. There's a great version with multiple voices.

My approach: he will read all those books di jour like Percy Jackson or Harry Potter on his own. What he will not read on his own or in school are the timeless classics.
Therefore:
White Fang/Call of the Wild
I, Robot
Space Cadets
The Hitchhikers Guide to the Galaxy
Three Men in a Boat
Sherlock Holmes
The Adventures of Tom Sawyer (and Huckleberry Finn)
There is great CD series called Classical Kids that tell about composers and play their music
Lord of the Flies (but only if not narrated by Golding himself -
It’s horrible narration)

And yes, a lot depends on the narrator.
For example Three Men in a Boat shouldn’t be narrated by Hugh Laurie (one would think, right?)
Anything narrated by Mark Turetsky is great

Good luck!

Ready Player One
Dune
The Martian

My kids loved the Artemis Fowl audiobooks.

Ready player one

Peter Clines - 14

scary but the time will fly by

Band of Brothers--depends on the age of the tween
I found this to be fascinating on a road trip from FL
to MD

Agree with a pp that the Percy Jackson is great, very entertaining. The sequels to The Giver are also pretty good.

Scythe - Shusterman

If you want to try some non-fiction... "At Home," by Bill Bryson