From a non-parent...
...who is, however, a step-granddad to my stepson's 7 year old: I hate them, even though I understand that under some circumstances they can be useful.
[rant on ]
I hate the fact that you can't go into a family-priced restaurant without seeing TV monitors everywhere. Really, are we so attention deficit that we must be entertained with flashy colors at all times while awake?
I know I'm getting into "grampa Simpson" mode here but I'm glad we didn't have those when I was a kid.
Those long road trips were some of the best memories of my life. Dad taught me to read a road map when I was about 8 or 9 and then I became the "navigator" on long car trips. Dad, being a historian, would always tell us about the history of the places were were traveling through.
Four years ago, wife and I took a road trip to Yellowstone NP with my then 11-year-old nephew, who had never been there. We established one rule from the beginning: No movies, no iPod, no gameboy. We got a couple of books on CD and listened to them, and we tried as much as we could to engage him on the trip discussing the history, geology, and the natural beauty of the area we passed through (we went through Rawlins and Lander on the way to DuBois for our first night, and returned through Cody and Thermopolis.) Wife also taught him how to use a SLR camera.
Was it a success? Well, I think he was glad to be home after 4 days and he hasn't asked to go on any trips with us again (though to be fair, we haven't offered, either.)
I would personally counsel parents to strenuously avoid the ubiquitous DVD player if at all possible. We're way too video addicted as a society as it is, we don't need television (or for that matter the internet) everywhere we go. This country is way too spectacular and beautiful to miss it watching a silly movie on a tv screen.
Sorry for the rant, I know I didn't answer the question the OP asked but it's something about which I have strong feelings.
BTW, my now 15 year old nephew lives less than 10 miles from some gorgeous mountain hiking, biking and other great activities. And as far as I know, he's never - ever - been up there to see or participate in them. Nor does he seem to have much interest. His parents (my sister and brother in law) live on a golf course and that's their idea of outdoor recreation. I'm pretty sure my nephew has never been camping in his life.
OTOH, he's great at video games.