Make up some games. My sister and I drove from Michigan to WDW in 2005 and to keep ourselves entertained we made up games because it made us use our brains and stay alert.
One game that we play is kind of a 20 questions. We usually do a movie theme. One of the rules is that I have to have seen it since my sister is a movie nut and has seen tons of movies I've never heard of. So she will think of a movie title and I can ask 20 yes or no quesions. Then we switch. You could easily do a Disney theme version.
We also sometimes do chain games where we pick something we see along the road then the next person has to find something that starts with the last letter of the previous object/thing. This can be quite challenging if you are in an area where there aren't a lot of billboards/signs and you need something that starts with a Y.
On other trips we've taken Mad Libs to do, using again things we see along the way. Of course some of ours aren't appropriate for children, but they are fun nonetheless.
There is always the liscense plate game. Have one of your children keep track of all the states you see.
Of course there is always my parents favorite game: the quiet game!
We used to play that one in the car when we were on our way to Florida.
Something that you could do for the older kids is maybe look up on line information about the states you are going to travel in so that as you drive through them you can give them a little of the history of that state or area. Maybe even ask them if they know what the capital, etc is. Though they may not know that. Just a way to make it a bit more educational.
Make up your own games to play though, that is my suggestion. Find ways to tie in what you see around you with the game will make it more fun.
Have fun and safe driving!
