I would probably mention it in conversation if she asked how your family was and 'blame' the psych for a) having a party - normally you don't but she thought it would be a good idea to introduce him to school buddies and b) she's suggested that you don't have too many people so you have to limit it to school people and there's lots of family/friends who will miss out.

So if it comes up in conversation, I'd treat it like it's a bit of a drag but something you have to do to keep the psych happy.

Conversations about her boys' behaviour can wait for another time I reckon. Too much of a double whammy to say they're not invited and by the way, it's because they're aggressive.