The Mt. Rushmore thing is interesting, but because of the altitude restrictions you really don't get the best view. If you have never seen it, I would land at KRAP and drive up for the better view.
If looking for other things to do, there would be: a weekend at Mackinac Island, Niagara Falls, New England in the fall for the leaves, Maine for some lobster, the Bahamas for just about the most beautiful place on the earth, Taos for the art crawl in September, Denver for the mountains, Kalispell for the continental divide and maybe some trout fishing, Missoula for a little fishing on the Clark's Fork. I guess that's about all I can think of for now.