Not sure how long you've got in total, but this article from Outside magazine, published in 2002, might still hold some useful nuggets for your trip: http://outside.away.com/outside/destinations/familyguide2002/park_bagging_1.html. Plenty to do in between, yup. But if this sounds like too much driving, my gut says stick to the Yellowstone/Grand Tetons beat as there is SO much to do around there, especially if you have kids who are into hiking, camping, rafting, and wildlife!