A boundary regarding contact with OM at church would be unenforceable.
Why? It's a choice your wife makes.
If your D says that she sees the OM at church, then she can go stay with him. She gets to make a choice -- your family, or him.
If you articulate the consequences of her choice, then you can enforce them.
Me: 44, Wife: 39 M: 17 years T: 20 years Bomb on 08/25/09 1/13/10: MC started 1/28/10, 2/8/10: More bombs 8/28/10: Wife moved out No talk of D, no movement