Not a bad experience if you are prepared. Books, crayons, coloring books, movies, video games, snacks, drinks, a few toys and you can't go wrong on an 18 hour road trip. If you want to pack light and if your kids are anything like Sesi, just take a video game and you won't hear a peep from them the whole 2 day drive. They won't ask for food, or water, just the game and the occasional bathroom break and they'll be good.
We didn't know what to expect on such a long drive, but the kids were great! They like to travel and it was all very exciting for them. The 2 youngest boys, no fussing or crying unless they had dirty diapers or were hungry. I couldn't have asked for better road buddies.