Oh I guess it is off the beaten path. We live in Oklahoma, so it was on our way home I guess. You're already trying to fit a lot in one vacation. I guess I'd leave it for another time.
We've done a ton of ranger-led activities at Yellowstone and Rocky Mountain National Park. I highly recommend them. My kids always loved being outdoors and learning about animals and such. Ask at the visitor's center for a list. They'll also give you a list of hikes. You might want to choose some easy ones. We did an awesome night hike at RMNP that we're all still talking about. It was around a lake without flashlights - just the light of the moon. The ranger taught us about using all our senses and by the time we finished the stars were all reflected in the water. Ah, it was beautiful.
As far as Yellowstone, it's a big loop. Don't try to do too much in one day. Read about the areas that might interest your family and do one section at a time. In the summer, traffic can be tight. So do one area, and then the next day move on to the next one. Otherwise you are driving too much of the time. It takes several days to see even the high points in my opinion.
My son loved the mud pots and geysers (for a while). At one point we heard him mutter "More mud, more hot water!"

Most of these are along boardwalks, so they are easy to get to.
He was fascinated by the wild animals. If you hike - wear bear bells so you don't surprise a bear. And learn safety procedures in case you have a wild animal encounter. We saw bear, moose, deer, and bison among others.
Mount Rushmore is pretty cool, especially at night. I think they also have a show in the evening? Not sure. It's been a while. Watch North by Northwest before you go and you can pick out where part of the movie was filmed in the restaurant.
I'm not as familiar with Jackson Hole, but I think they have a ski lift type ride to the top of a mountain. That might be fun. I've been through there, but have never stopped for a real visit.