Her ex, reconciled with kids, is a threat

There is an argument to be made that you may reclaim your power in some way by confronting this fear, but this choice is not for anyone but you to make. The opposite side of this argument is that you are plenty powerful by choosing to stay away from someone who has abused and stalked you. I give you credit for reclaiming and rebuilding your life.

Your kids are in no position to gauge this man's behavior or the effect of his alcohol use. The idea that you would somehow be safe if he is kept on the other side of the room is bunk. It simply discounts the very rational fear response toward danger.

Your children have every right to have a relationship with their father, but you have a right to keep your distance.

Let them know that you expect them to notify you if their father will be present at a family event.