Lived in Rapid city for a few years and have been back many times. We generally stay at the Air Base but think Rafter J is the go to campground. Popular so make a reservation. We didn't think much of the Rapid KOA but it is conveniently located and close to shopping. Avoid early August bike rally as mentioned whole area turns into a huge traffic jam. Deadwood with the gambaling has turned into a tourist place a real shame it was great before. Wall Drug is a tourist trap but a good one and never pretended to be anything else. Crazy Horse is also not what it was and costly but still worth a stop. With only a couple days you won't be able to do all the major attractions but with a little planning you be able to choose the ones that interest you.