Lunch with kids yesterday

Well I have told 3 out of the 4 kids that their dad is an alcoholic.  Funny thing is I am late to the party - they had already figured it out!  I am not sure how I could have let this creep on me, except that I must have been in total denial that he had a problem.
Now I am struggling with the next step, which is divorce.  I don't have the heart to tell him or the kids - but I know it is the right thing to do.  Neither one of us will be healthy unless we get away from each other.