I just got back from a trip to Disney with my kids -girl 9, boy 6- and wife...older.
We drove from Ottawa, Canada, 24hrs total drive time. The time was split 75% to 25% infavour of Harry Potter audio books over music. The music winner for over-all satisfaction for my kids was ABBA followed closely by the Beatles Abby Road. For my wife and I it was Emmylou Harris and Mark Knopfler- seperately and together. I have to say that kids, in gereral, do not respond well to the lyric alone. If a lyric is delivered in a highly melodic or highly unusual way (I am the walrus..goo goo goo joob) then they get interested. My daughter also is a big Sheryl Crow fan and likes her version of Dylans' "Mississippi" so I played her dylans Mississippi, one from a few years back and from the latest bootleg CD, and it had almost no impact even though dylan's delivery is much more meaningful. I tend toward classic stuff that is strong on melody and good musical form for my kids. 80% of the time they dig it.
I teach guitar and music and what I find interetsing is that kids today- the ones wanting to learn about music anyway- are listening to the stuff I grew up on in the 70's. I had a 17 year old student actually request that I teach him an old Lindsay Buckingham tune from before Fleetwood Mac. That floored me.

Even more shocking is that I remembered how to play it.