Knowing my daughter would be involved in this mess would probably stress me out more than if it were me. If its my wife, then that's the same as me.
If its really not your thing to go out there anymore, then dont. War with the family, or not. If things were all roses and unicorns and everyone was happy and agreeable and one big happy family, that's one thing. In that case I'd say yea suck it up, keep the peace, and go out not every time, but every now and then, and pretend to be glad to be there, because they're good people and it makes them smile. But delusional, enabling, lazy, money leaching, substance abusing.... who needs that?
PBbbllllltt. You'll have to balance this out with how your wife wants to handle things, but back out every time you can. Honesty, dishonesty, you're in sanity preservation mode at this point. You don't enjoy it, its too much work, its not your thing, etc. Sorry folks, I think we'll take a rain check this time. And next time. And next time....