Girl Next Door, I seem to have written a giant tome, so I’m going to break it up into a couple of posts.
I don’t think you should beat yourself up over this. It’s a new, odd situation, and you’re not comfortable with it. That’s entirely reasonable. Don’t feel bad about that.
You’re entitled to your feelings. (Og, that sounds way too new-age-self-help-gaga!) But it’s true.
I’m glad to see that your husband is going to discuss this with his friend, I think that’s the right route to take.
I would recommend sitting down with your friends and telling them how you feel. Don’t try to tell them what to do, or that their behavior is unacceptable - that would more than likely just piss them off and end all possibilities of a good solution.
But it’s perfectly legit to say “This is all new to us and we’re very uncomfortable with this situation. For instance, it makes us very uneasy to see you being physically affectionate with other people. We understand that you’re all fine with that, but it bothers us a lot. We’re trying to come to terms with it, but having a hard time. Just wanted to let you know what was going on, in case you picked up bad vibes from us.” Not judgemental, not accusing, just being honest about how you feel. And it’s perfectly OK to do that just with your friends; you don’t have to include their new people whom you don’t know in your private conversation. Those people are not your friends yet and you don’t owe them anything beyond normal politeness. (Of course, your friends will talk about it later with them, but you don’t have to.)
If they’re reasonably nice people who care about you, they’ll probably tone it down a bit until you’ve had a chance to adjust. If they don’t, well, at least you know where you stand.
If you don’t want to invite the new kids to your house, then don’t. But don’t be surprised if the group as a whole declines to attend. I certainly wouldn’t go to a party or event (outside of work or something similar) if I was told that only certain members of our family were welcome. We’re a family and come as a unit. Like it or leave it, it’s up to you. [ETA: that doesn’t mean we’re joined at the hip or anything. I’ve skipped several “high school reunions” because I’ve got no interest in listening to people chat about events and people from three decades ago that I’m not familiar with. But if someone were to actually say “redtail, we’d like you and SO1 to come, but you can’t bring SO2 because that’s not a valid relationship and we don’t want her there” - well, chances are pretty good that you wouldn’t be seeing much of me in the future at all.
There’s not much you can do about parties at other people’s houses, except decide what’s important to you. I have friends who have friends that I cordially detest and would much rather never hear of, much less see, again. Those people don’t get invited to my home. I don’t attend events at their home. If I know that they’re going to be at a third party’s event, I decide whether or not I want to deal with them in that situation at that time - I may or may not go depending on how I’m feeling, who will be attending and how much I want to see them, if it’s a large party where I can just ignore them vs. a small gathering where I’d be more-or-less forced into interacting, etc. If I don’t know ahead of time, I decide on the fly depending on my mood and the situation. I’ve left early before to avoid dealing with these people.
Sounds like you need to do something similar. Which is more important to you - seeing your other friends, or not seeing the new people? Are the circumstances of the event something you can deal with?
You can’t change their decision to bring along their new loves, all you can do is decide how you’ll deal with it. OK, you can try to force them to live on your terms by insisting that they should attend but not bring their SOs, but I doubt you’ll have much luck with that.