We liked Acres of Wildlife in Steep Falls, ME. Yes, it is out-in-the-middle-of-nowhere but it is a fully equipped camping resort. It is right on Rainbow Lake which has a gentle sloping beach for the youngest swimmers. My favorite memory of that place is the many dragonflies and damselflies that would alight on you like the most delicate jewelry. It would explain why we never saw a single mosquito despite being across the road from the lake. It has an awesome playground too.