I hear you there. Im sorry to hear it. You sound like you're in the exact same situation as my mum.
My addict brother met a trashy alcoholic girlfriend out of rehab, against the sound advice of lets see, EVERYONE around him. Weeks later, he had the nerve to get my father out of bed at 3 AM to pick her up from the police barracks after she was arrested for DUI. Not only is he using again but SHE is too now. They've since stopped enabling. (almost)
I stop doing stuff for ungrateful people ANYWAYS. I would do it 10x quicker if they were an addict. So sorry to hear this. I think you have a good idea. You can't stop them from spending time with one another but you certainly dont need to compromise the peace in your home by making it a venue for chaos.
take care of yourself