My husband and I would like to take our son to see Yellowstone, Glacier and Grand Teton Parks next summer. He's ok in the car for a day or so but then complains. If we flew out from the East and rented a car that would cut off some driving time. I know how big YNP is as we've been there twice before without children. For those of you that have travelled with 15 year olds, please help us. I know there's fun stuff like the horseback ride/cowboy dinner, lots of widlife viewing, etc. He says he's not much of a hiker. I'd really like him to see Glacier before all the glaciers melt too so this trip would combine that park to. I'm thinking of about 14-16 days. Advise please?