We are taking our grand kids to Yellowstone. We have two weeks with a week in Jackson Hole. Our grand kids are 12 yo triplets. What places would you recommend within a reasonable trip from I90 that are must see experiences?

That's a nice drive. Check out my trip report from a few years back for some suggestions:
http://www.fodors.com/community/unit...roit-to-ca.cfm

Have fun!

Very touristy, but the Corn Palace in South Dakota is worth at least a photo. Also, Pipestone Nat. Mon. in MN, Badlands Nat. Park, Mt. Rushmore, Devil's Tower. Little Bighorn Battlefield, Pompey's Pillar and the Yellowstone River Valley from Billings into the park. If you want to go a bit out of your way, "The Pit" in Butte, MT

It's hard to remember, our trip was at least 15 years ago, but I think we made it from Chicago to Rapid City, SD for our first night. Visited a museum in Rapid City, native American info and dinosaur stuff? (memory is a bit foggy)

Glad that you are spending enough time at Yellowstone to see several different areas of the park, it's amazing! Each day we did a loop in a different direction.

We were lucky to see "Grand Geiser" go off, much larger than Old Faithful, but not as regular. We were on a hike and came to a spot where a lot of people were waiting, they had books on geisers and could tell by 'signs' that Grand would go off sometime within 24 hours. We waited 3 hours, it was worth it!

Wall Drugs is of the biggest tourist traps in the world, but going there and getting ice water is free. May as well as get the photo and the water.

Also, do NOT miss Badlands NP, Mount Rushmore Nat Memorial, Devils Tower Nat Monument, or Crazy Horse Monument.

I made the exact same trip several years ago. Off the top of my head, the Badlands and Mount Rushmore were the highlights.

And if you're up to it, take them rafting in Jackson Hole. It was a really neat experience.