Books, movies, music and games are all ways to keep your kids quiet for a longer period of time. To get your children excited about your trip, have them pick out a new book or movie they can read or watch during the ride.
If you have younger children, bring a V.Reader and several book cartridges they can read on the trip. A portable DVD player with a new movie can also be a big hit. Handheld electronic games can keep hands occupied. Let your older children zone out to their favorite music on their MP3 players.
Be sure to bring headphones for these electronic gadgets, or your trip won't exactly be noise-free. Also make sure your electronic gear is charged up or has enough battery power to last for your current leg of the drive.
You may also want to consider limiting "screen time" so that you have enough opportunities to connect as a family during the ride.