ROTFLMAO!
After a Custer Park, Rushmore, and Crazy Horse loop the first day, we always take first time visitors to Wall Drug, then back home via the Badlands.
After that, the rest is up to them as to what to see & do.
Wonderful place, South Dakota. I visited twice on the way to California when I was a teenager. I'm looking forward to taking my kids when they are old enough to appreciate it.