It's not an easy decision to make. One poster recently said "I have to come up with a reason for leaving him that he will agree with (or understand)" and that really resonated with me. I had such a need to be right and to make my husband UNDERSTAND why I couldn't do it anymore (because then, maybe, he would change).
It was really hard to come to a place where I said "I am just not going to live like this anymore. And my children aren't going to grow up thinking that this is how people treat each other and all twisted and warped as a result of this alcoholic dynamic in their home." But thanks to support from friends, family, and detaching enough to trust myself, I was able to end it.
Now, having said that, it isn't true that there is no going back. If, in 2 years, he presents himself to you in recovery, and having put his life together, you can always reconcile. I wouldn't tell anyone this - it's just for the benefit of you. It isn't conditional, but IF that happened, you could always consider reconciliation.
You are a good mom, but it's time to put your peace and your children's peace first. Good luck to you.
eta: lillamy's post. Yes.
I have some difficult financial decisions to make, but the peace and ease and lack of a battle zone in my home - irreplaceable.