Thanks, Gerda, job and sjohns6. As always, sage advice.
I should clarify that I wasn't really thinking of adopting a hardball strategy. I'm more wondering about making a decision to take my son to the city. I'm considering doing so to remove myself from the situation (having this happen right in front of me in this small town is rough). But I don't want to leave my son with my wife because I think he would end up meeting the OM much sooner. And a man who can take advantage of a vulnerable married woman--when he has nothing to lose and she has everything to lose--is not the kind of man I want in my son's life. So this is more about protecting myself and my son than it is about trying to affect my W. But she's already rejected the idea, so I look at my doing it over her objections as playing hardball.
My guess, based on what everyone is saying, is that it won't change a thing. If that's true, great. I'm just worried that she might view it as punishment, even though I gave her the reasons mentioned above. Of course, she defended the OM as the embodiment of noble man, but that's just the fog talking.