Great campsites! Many are a short walk from a nice sandy swim spot. Lots of great shallow areas along the shore, fun for kids. Watch out for slick spots of clay, though. Tell your kids the clay is nature's play-doh, and they will keep busy for hours! Most of the sandy areas are really nice, fine sand. If you get a windy day, the lake will even give you waves.
NOTE: Some spots say online that they can accommodate a really large size camper, but require expert level maneuvering to get in and out. OR, may have loose gravel or untrimmed trees that make it impossible. Call and chat with the park ranger if you have a plus size rig, just to make sure your chosen spot will be appropriate for your camper!
ALSO: Like most parks in Oklahoma, there is a TON of poison ivy. My kids are well aware to stay away, but if you or your kids can't easily recognize it, check w the park staff. Stay on pathways.