They'll be fine. We traveled 1100 miles, over 4 days (took our time, since we had 4 rats, a dog and a cat at the time, and had to stop at rest stops often). We also transport a lot of rats.
A smaller cage for travel (cat carriers work well) will do you good, and be sure to belt it in. Don't put them on the floor in a car, especially in the front seat (fumes can get to them and they can die from inhaling them). Leave off the water bottle so it doesn't leak, and give them drinks whenever you stop. Also, provide some fresh fruit with a good water content. Make sure they won't be directly in the sun, and give them a place to hide out (soda box works fine). They'll probably sleep most/all the way.
I took my rat with me on vacation. It was a two hour drive. He didnt mind it at all. He slept most of the time and every once and a while would pop his hed up and look out the window. Try to travle at a time your rat is ususly asleep.