Mt Rushmore has some very good fireworks done so they look like they are over the monument. The locals sit on the hill side facing the monument from the turn off to keystone. get there early Parking at the Monument was $8 last time we were there
Lead has a great display usually done on a different night , in the gold mine pit - Sit across from the mine on the hillside over the carnival with all the locals.
Rapid Citys Display is good as well
From the Black Hills the badlands are a short drive about an hour if I remember correctly as is Devils Tower Both worth a look. Badlands in the summer get HOT.
Custer State park is very nice. we saw the most animals in the early morning, just after sunrise.
Reptile gardens and bear country USA both tourist traps that we stop in every time we go.
Spearfish canyon is enjoyable the falls are nice and worth a picture or 12.
If you like trout, a non res fishing license is relatively inexpensive for a 1 day or a week long one. Lake Pactola, north end of the Dam there is a parking area anywhere along the point with your back to the dam is good
Link to black Hills Map
http://home.nps.gov/moru/planyourvisit/ ... %20Map.jpg
I like anything that turns money into noise.