We were invited to an end of year party out at Buford Dam Park (just past the dam itself).
The park had a playground, picnic area, volleyball area, soccer area..
and beach! We were somewhat surprised at the lack of people out there, but really didn't mind. For $4/car, it was a wonderful outing for the kids. They splashed in the lake, had lunch, and in general enjoyed their last day of school.
It's a place we're going to keep in mind potentially returning to during the summer.