Can't recall where Church Bay is but all of Anglesey very nearby (are you in a car?) There's a model village at Newborough which we thought was reasonable value. The beach at Newborough is good, but to drive down you have to pay. There's also a forest walk down there.
Thinking about it I think most things we've done on our holidays in Anglesey have cost money, other than the usual beach and walks, so I'm not sure I can think of much..!