Lewis and Clark recreation area and Gavins point Dam in Yankton South Dakota is a must see as far as camping destinations.  It doesn't have the kid friendly amenities like Mahoney, but the park is beautiful and meticulously maintained.  Many of the campsites have direct view of the lake and are right on the bike trails.   My first day there, I saw the bathrooms cleaned.  This included pulling out the shower mats and hitting them with a power washer and disinfectant.  They also came by and cleaned out my fire pit and were mowing or trimming trees the whole time.  There is a lot of care that goes into the up keep. 
If you want peace and tranquility with a beautiful view then I would recommend this park.  There are also plenty of playgrounds for the kids and several swimming beaches.  There is a nice marina with a restaurant and also cabins to rent if you prefer a little like home accommodations.  Yankton is a very nice town with lots to do and is right nearby.
The only downs side that I can think of is that the bugs were terrible.  Especially the gnats.  They will swarm you as soon as you step out.  Maybe this was just the time of the year that I went (late May), but either way it was very annoying.   You will need to a good campfire to keep them away.