So I suppose someday it will be very easy to take a road trip, you know when then can entertain themselves and I don't have to be involved in every decision. Until then, road tripping is tricky, but possible. When I came home from the beach, I was by myself with the three kids. Beyond the crutch DVD player (which yes, is wonderful on a long trip) I make sure each kid has a snack in a portable cup with a top and their own nalgene water bottle (which pretty much stays in the car). Course at the baby stage that my Little Sausage is in (he's 5 months old) snacks mean Mommy, but that's another story. They each have an old wipes box that they keep in the car filled with small toys. For long trips they can each pack a backpack with toys.
I go to the library and get a bag of 10 books (and keep the receipt so I know which books to return)and get a few new trinkets that I break out as the ride goes by. I also really like using a travel tray for the Banana Girl since her carseat doesn't have anywhere to sit anything. Super Bear in the back has a whole backseat to use as his tray.
For stops, we love Cracker Barrel, where they love exploring the store and rest stops to run around and potty all together in the family restrooms.