I will bite-
both our kids are mid teens at this point. We have traveled 3.5 hours north and 3.5 south for each of the last 14 years.
roadside scenery is NOT important to kids. they can go by the most beautiful mountians in the world with not much to do an dstill they are not mesmerized.
before they could read, coloring, some books on tape, some conversation etc. - music- some of theirs, some of ours
the ride south- SLEEP.
after the age of 5 or 6, add reading
after 3-4 grade- add some homework
after 12- they have plenty of conversational topics, and if you take they time- there is plenty to learn from them about what is really going on. And the homework starts to really ratchet up (ok, normally only on the ride south)
to each his/her own, but my wife and I have never regretted our position on this. Our kids are avid readers, like lots and lots of differnet music and we feel we know alot abouot their friends both at home and on the hill-
good luck and enjoy the ride-