I live just outside of Denver. After you pick your friends up from the airport, which direction are you ultimately going? Cherry Creek is a nice park, I've never camped there, but it's not that easy to get to from DIA. A lot of traffic and road construction on I225 towards the park.
Closer and easier might be the KOA in Strasburg. It would be east of DIA. Not sure how far east. Or stick with the Meadows RV park in Aurora. Cherry Creek is in the middle of very populated and commercial area.
ETA: Didn't see you were headed up to South Dakota. I think I'd stick with KOA Strasburg or your meadows rv park in Aurora.
