When my son was four he was a saint traveling. I suppose he spoiled us, because my daughter isn't so tame. While my son is content to play his Nintendo DS, or read a book, my daughter wants something new to do every ten minutes or so.
One of the greatest forms of child entertainment ever invented for people who like to travel with their children, like us, is the portable DVD player. You just plug it into what used to be used for lighting cigarettes and voila, instant entertainment.
Thirty minutes into the ride and we found our DVD player wasn't working, so we already had to make a pitstop -- at Walmart.
So, we made it. It's warm and sunny.