Ro... I get where you're coming from but realize you really don't have a ton of control here.
If OW tells SS what will you do? Divorce your H? <ok... a little tongue-in-cheek there, but see my point?> Not talk to the OW?
You're right of course... your H and you need to tell your SS. He needs to hear it from you two, together, and not from the OW.
So then... since you can't control the OW you can only control what you do. If you think he needs to know, now, then you need to control your life. H can come along or not.
He's chosen to make these beds to lie in... don't let him make you prep the beds too.
Stop trying to control people you can't control. Control you. It will make you less crazy. I promise.
Married 6 together 8 Me:38 W:31 second marriage for both SS12, SD10, S6 Bomb: 9/8/11 (day before our 5 yr ann) W moved out: 2/18/12 D final: 11/12/12 Share S 50/50. Spend as much time as I can with SS & SD