Going to South Dakota we go through Custer Park and on to the Mammoth site. It is the best ever for the family, the kids love it, you must make advance reservations for the kids to dig. There is a small digging spot for children, my grandson was so disappointed the first time we went.
The tour is awesome The site is indoors so it is air.
Wear shorts & tee shirt, pack a cooler take water, there are plenty of trees for a picnic,
after the tour.
You are really going to enjoy this... have fun.