Must See places for kids

California and Oregon are indeed a long drive and I was a bit apprehensive before we made our trip a few years ago. DW and our grandson had been pressuring me to take them out west for some time so I decided (summer '09) I was going to do it. We left Kentucky and went down through Tenn, Ark, Ok, all the southwest and up the Pacific coast to Washington and even into Alberta. Of course this takes some time but I believe you can do it with minimal planning. I had NO reservations since I always left it to DW to decide when to stop and when we did decide to stop long enough to require an rv site we had no trouble getting one. We saw some things/places we may never see again but I won't have to live the rest of my life wishing I had made the trip.
OOPS, sorry I didn't see the sentence where you had a 1500 mile limit but good luck all the same.