Thank you so much for sharing what you are going through. I cannot imagine becoming a single parent as a result of my spouses alcholism (or drug addiction). How difficult that must be, I can only imagine (financially/emotionally, etc.). I have no doubt the children are confused, in denial, etc. My thought regarding that (just in case I might be right...), is not to demonize your husband, their father. That will only harm the kids.
No matter how frustrated/angry, you might become with your spouse, please do not ever say to the children, that their dad is a bad person in any way. Tell the children all the good things you can about him, and explain that he is addicted to alcohol. Let them know "anyone" can beome addicted to alcohol. That he is NOT a bad person, but his mind and emotions don't function right as a result of the alcohol in his system.
Kids (subconcioiusly) believe they are half one parent, half the other. So telling a child that their parent is weak/bad/hopeless, etc., won't do anything but hurt the kids. It also won't help your spouse.
Please write anytime. Hope I didn't overstep with my thoughts. Keep the kids from feeling ashamed of their father...