We camp at many of the state parks within a couple of hours of Des Moines and I can say for the most part, they are quiet and well kept. Some of our favorites are Springbrook State Park, Ledges State Park, Clear Lake, and Lake Anita.
Every county in Iowa has campgrounds as well. Some of the central ones that we prefer are Pammel Park (Winterset), Spring Lake (Jefferson), and Don Williams (Ogden).
Take Highway 169 through the state, or Highway 6, both can be scenic and charming. I have heard great things about the Mississippi river area of Iowa, but I have't visited there yet.
If you like to golf, you won't find it cheaper any other place. The state is relatively flat, which makes towing nice. The food here is cheap (relatively) and very good quality. Eat your way through the state.
Feel free to PM with any specific questions, I live in Des Moines, so I can answer almost anything central.