Thanks for the feedback!
Dick_B, you landed on my concern - keeping the kids engaged and happy. They need so much stimuli! I will say, we are into hiking, whether you measure it in distance or time... We will be in Yellowstone for 4 days, I only plan a couple trips into the park. I am content with sitting by a fire or splashing around in a river/lake/pool. I have done a few trips like this, I have learned a few things over the years. Plan a lot of stuff in advance - the things we will do and some alternatives, let each kids pick their one thing, make some time for individual interests, be willing to change plans with a moment's notice. I also implemented both technology free times or zones and down time/lazy days. I have come to the realization that every post card already has a better photo than I can take. I take some "fun" ones with the kids, not too worried about the perfect shot anymore.
Mt Rushmore is more planned with more detail. We are only visiting the Mt one afternoon, will stay late if they have fireworks this year. We have a chuck wagon supper and show, gem/gold mining, horse tour, Wall Drugs, maybe Sturgis or the indoor water park.