Thanks for the quick responses, and I welcome even more opinions. Are there any recomondations for motels, near Fayetteville, or lumberton?
OK, here's the answers to the questions you didn't ask.
1. Pack a smaller carry-on style bag, and put it under your child's feet as a foot rest. It will help keep him more comfortable, without the dead weight of legs pulling on him for hours.
2. Pack his favorite lunch in a cooler and picnic at a rest stop. It saves time, and it keeps his system normal (predictable) on the road.
3. Think about a variety of media to get through the day. We always get one or two beautifully illustrated books that the adult passenger reads, and for each 2 page spread, hand it to the back seat for both kids to admire the artwork. Depending on the book, this can take up to an hour, and the adult isn't having to read exhaustively.

Also, consider an audiobook, which you should be able to download from your library. I find the audiobook is always better before breaking out the dvds. YMMV, but I find the later hours in the trip where everyone just wants to zone out and enjoy a favorite movie.
4. Wiki sticks or colored pipe cleaners...this will depend on whether or not your son likes to make "sculptures". We have made some seriously weird things on the road. It would be a stretch to call it art, but it passes the time. And, my kids enjoy it...
Oh and if you end up in Fayetteville in the afternoon, here's a place I bookmarked, but have never gotten to visit:
Monkey Joe's. Or if you pick a hotel with a pool, that should get your child's blood moving again, too.