Oh my gosh, what a punch in the gut!
I'm thinking your 17-yo DD is legally old enough to choose not to go on this vacation.
I'm thinking you need to talk to a lawyer tomorrow. Immediately. I'm thinking you need to do a cash grab & set up an account for yourself. I'm thinking that you might have a legal leg to tell your WH that no, he's not taking the kids on this vacation, that it would be very damaging to them psychologically.
I'm thinking you need to get your kids in to see a counselor immediately.
Gently, I think you need to get off your youknowwhat and take some action. You say you're codependent? Okay, I know all about that. I know that one way to rid yourself of that curse is to take action. Do something!