Hi Katchie,
I would suggest that when he shows up, you immediately set your boundaries and rules. Lay it out there so he knows that there will be ZERO tolerance for his drinking and stick to your word....
Both you and your children deserve and need a sober life. While I truly hope that he will see the error of his ways and get and stay sober, PLEASE do what is best for both you and your children.
I know what it is like to live with an alcoholic father. Every day, mine would walk in the house already drunk... with a fifth of whiskey in his hand. Yes, EVERY DAY there would be a new bottle!! He would verbally and mentally abuse my Mother and my Brother and I until he passed out for the night. The trauma he caused eventually contributed to the suicide of my brother. I live with lingering effects of his behavior to this day.
I can see that you are holding your children as your #1 priority, PLEASE continue to do so.