I don't want to put a damper on all of this, BUT it sounds like y'all are going to try and 'intervention' and it sounds like none of you are on the same page, and he does know how to manipulate all of you.
He is telling you who he is, BELIEVE him. Do you want to spend the rest of your life like this? If not, then go for a trial separation, no he cannot come to your house, no he cannot talk to you and the kids. Set a time limit, like one year (yes that seems like a long time but it will take a year, no matter what 'program' he uses for him to get the cobwebs, fog, and mush from his brain and start working on him) to see what his ACTIONS are, not his words, but his ACTIONS.
Oh, and btw, this applies to you also. Let your ACTIONS be what you say, "walk the way you talk."
Trying Al anon, but it's a little to Godly for me at times.
Try about 6 'different' meetings to see which ones fit you better than others. As to the 'Godly' thing, some folks do use a 'Christian' God, however, the program itself is a Spiritual' program, and nothing to do with religion. You Higher Power can be whatever you choose. ie the Universe, Mother Nature, etc
If Alanon turns our to be not for you, check into getting yourself some private one on one counseling so you too can work on you.
It is absolutely your right to have a 'toxic' free home.
It is alright to have your personal boundary be: "I will not live with nor associate with anyone in active addiction or in the first year of recovery. I will not allow toxic people into my life."
It is okay to tell him your personal boundary or not. That is up to you. The boundary is for YOU.
Sending healing thoughts and prayers for you and your whole family. I will ask Great Spirit to guide you and his parents in this meeting y'all are about to have.
Love and hugs,