We've driven four times (about 17 hours) and flown once. We'll drive from now on. Flying was quicker, but driving was less hassle and a LOT less money. Even at $100 RT, it added up to $500 extra dollars for the 5 of us. Plus, we rented a van which cost another $200+. OK, by the time we take out gas and a motel room we don't save the whole $700 by driving, but a good bit of it. And with flying I ended up just as exhausted (or even more so) after lugging luggage all over the airport, getting up at 4AM to get the airport early enough, etc.
My older kids (10yo and 8yo) are good travelers. We listen to books on tape all the time (not just when we're traveling) and it really helps pass the time in the car. My little one has not been on a really long rode trip since she was 5mo, but I'm hoping she'll be just as good.
BTW, we're currently listening to Madeleine L'Engle's A Wrinkle in Time, which I've just heard is being made into a mini-series by Disney/ABC. It will be on TV next September.