There is nothing wrong with setting boundaries. Nothing.
You do not need a lawyer yet. See how the talk goes.
Plan accordingly to see if you can say what you need to say without emotion. My wife told me she always knew I was dead serious when I was calm, my wife said that she knew when I was strong in my convictions because I wasn't emotional.
Your daughter...get her a C. If you or your husband has any benefit package they usually have a plan that includes up to 6 free visits regarding mental health. That almost always includes family / dependants.
Be honest with your H about the concerns you have regarding your children. It is in your (you and his) best interest for their (children) best interests to be honest with each other. Tell him honestly that you are not doing this for any guilt or repsonse from guilt. But a desire not to emotionally hurt them.
Grace,
Your strength and patience will be tested now. You have done so good fro so long, remember this is the hard and rocky path. Do not falter, it wasn't going to get easier, it might get harder, look to your feet right now, not down the road.
Experience is a brutal teacher, but you learn. My God, do you learn. - C.S. Lewis
Life is usually all about how you handle Plan B. - Jack3Beans
Listen without defending; Speak without offending - FaithinAK