Don't do it. I wholeheartedly sympathize with what you're saying but I don't think there's any way you (your dad, your "side") can do this and not alienate people. If you want to do it as a joke, the joke should come from your husband/his "side", but better yet don't do it as a joke at all. Yes I appreciate the allusion to him being under new management and how the jokes would all be in accordance with that and the t-shirt and I think it's a funny idea but I can see it going wrong. Not the t-shirt, that's funny - but the rest of it.
You are entitled to set new "rules" together with your husband for your life together, and he is the one who should talk to his friends - right now IMO - and so send them the message that you've made this decision together. There's no way you won't come across as a b1tch no matter how funny you/your dad are. I don't know you at all so I'll back off immediately if you say that I'm wrong, but somehow I suspect that you're not sure if you're entitled to make real "demands" - well, for a life together, you are (as is he). Wait till June??
I know this isn't what you asked and I'm sorry if I've put a damper on things but I swear there's no way you can win this. Either they take it as a joke completely and forget all about it, or they take it as new rules being set - by you and you alone. When in fact you are BOTH under new management:)