McDonalds -- because who wouldn't enjoy a chocolate shake?
DVD Players. I know why I took very few car trips as a young child.
Because DVD players hadn't been invented yet.
When you are in need of a break, I highly suggest looking up an elementary school -- they usually have great playgrounds, and during the summer they aren't usually in use. We stopped at several during the time we were in the car, and I have to say that it was one of the better ideas I had on the trip.
And find a hotel to stay in with a great pool. We totally lucked out at the Clubhouse Inn and Suites in Souix City - the pool was small, but it had two great water slides that everyone loved. If you happen to travelling to a place with a Clubouse Inn and Suites, I HIGHLY recommend it.
*Successful is stretching it a bit -- the first day wasn't too bad, but the other three days that were spent in the car were filled with the sounds of a highly distressed two year old whining "I want to get out of my seat!" Oh yes, it was every bit as fun as you imagine it might be. And by fun I mean a great exercise in not completely losing your mind while in a moving vehicle.