G.B.
You'll need to stop about every 3 hours, even with kids this age. They will be arguing and nit picking from sitting in the same position for extended amounts of time.
You will enjoy your trip much more if you make the stops and let them run around and play. Like stopping at McDonalds or Burger King for snack time and let them play on the playground for 20 minutes after eating. They will respond better and actually it will be a much more pleasant trip.