Sounds like you're doing the right thing. At bottom, it sounds, then, like you're struggling with the question of whether or not
you should allow him to make such a statement. You can counsel him all you like, but in the end, he is still his own person (as you well know). My advice (I don't know if it counts as unsolicited or not in a setting like this
) would be to let him whatever statement he finally concludes is the right one to make, and then let
him live with the consequences. And if people ask you how you could possibly tolerate such a thing, look at them confusedly and say, "Well he's his own person. If you have a problem with his actions, why don't you go ask him?" And then
go straightway to your son and say, "You should know that so and so said to me that they're upset by your behavior here today."
The goal with that isn't to shame him. It's to get YOU out of the middle of it. You cannot stand between his actions and their consequences. You shouldn't be the gatekeeper of secrets. And same thing with your wife. It's not your job (in my opinion) to be the go between between the two of them. If she wants to take a stronger stand, well she's her own person and she can deal with the repercussions of that, just your son can.
I guess I'm just a bit concerned that you seem like you're carrying a lot of stress and anxiety over what, frankly, is someone else's problem. Maybe I'm misreading you, and that'd be fine--good even. But if I'm not, then what I say might sound a bit cold, but honestly, it isn't your concern. You can't control other people. Just yourself. All you can do is give the best advice you can, solicited or unsolicited, and then let other people make their own decisions. And when they get mad at you or frustrated with your or stressed and start taking it out on you, you just politely give it their anxieties right back to them for them to carry. And if, in seeing that you are okay (when clearly they are not) they want to ask your advice on how to approach the situation, then you're right back to square one with the new issue: you can offer your best advice and let them do with it what they will.
I don't know how long it is until the wedding (and I don't want to flip back through thread right now to find out if that has already been said), but a shortish book you might what to read is
How Your Church Family Works. Really a great read, only $10 for the Kindle edition, and pretty much everything said about the church can be said about your own family.