I would choose Yellowstone with kids that age. All the geysers and other features have a nice "wow" factor.

jayne1973,
Exactly what would you suggest for a 7-8 year old.

I'm thinking of taking my granddaughter.

Myer,
We took our three girls when they ages 6, 9 and 12, to Yellowstone. The geyser walk near Old Faithful is easy and so full of interesting features. On the balcony at Old Faithful Inn, you can sit on benches with a beverage and wait for OF to erupt, which happens every 90 minutes or so. There's horseback riding at Roosevelt, and if you go in July (check dates) you could take the Chuckwagon Cookout ride (horseback or wagon.) We always went too early in the summer and missed it, which I still regret.

The loved it all again when we took them as teens and young adults, too.

jayne1973,
I know the park as I've been there but I may be able to take my daughter and granddaughter late July of 2014.

Looking to focus on things for her to enjoy as she still talks about our trip to Yosemite a few years ago.

Thanks. The cookout may be an idea but it's up near Roosevelt. I'm not sure I like the idea of driving over Dunraven Pass in the dark coming back to Canyon.

Sounds like a great trip for you all, Myer.

My only suggestion regarding the cookout would be to spend that night at Roosevelt. We always seem to end up spliting our lodging between a couple of different places due to availabilty, anyway. It is kind of nice of because we can plan our days and driving times based on where we are spending the night. Less backtracking.