I've been to Raystown almost a dozen times. Always loved the area. Lake Raystown Resort has RV sites, and has waterfront sites. They also have a small Waterpark for the kids, and various other types of lodging. We used to rent a houseboat there every year and spend a week on the water. Raystown may be one of my favorite places in the world.
If you aren't bringing a boat, then make sure you rent one. Maybe just a pontoon boat for the day. You can't really enjoy the lake to its fullest if you're not ON the water, you won't regret it.