Originally Posted by
CoParentToA 
I'd like to think that if I started to see signs that XAH was drinking, the sponsor would be in a position to reach out to him / offer support in a way that I myself would not be.
I have no personal experience with AA but in my opinion the advice you have been given here is really solid.
I'll throw in my opinion of what I see here.
Your plan may actually backfire in that if your goal is for your ex to remain sober having his sponsor in your "camp" voids any security/ trust between the two, ie: if he is thinking about drinking or actually drinking why would he tell his sponsor if he will discuss it with you? I'm thinking his sponsor would then be the second to last person he would approach (besides you).
It's an illusion of control that you don't actually have. Right or wrong that is how it is. In no way do I mean to trivialize your concern for your children, you are right to be concerned, I get it, however in this instance your control is only on your side of the street unless and until he shows his hand as drinking again.
-