We are going up in September this fall as well. We plan to stay at the Heartland RV Park located just off Highway 79 about 15-20 miles south of Rapid City. It is 100% pull through and they can handle any size rig. It's not the cheapest, but it is located close to Mt. Rushmore and has absolutely all hook-ups including cable TV.
2018 High Country 321MK
2017 Silverado 2500HD Duramax Diesel