I think that the Al-Anon book for children could work well. I read it to my boys. I'm not sure, but you probably could order it from their website.
I'm sorry that I have forgotten exactly what it says (and its title), but the gist is that the alcoholic is sick with a disease of alcoholism.
Your husband probably does want to be a good father, but he doesn't know how like my husband. It didn't get modeled for him.
I stayed with mine (husband), and usually told my sons that we love their dad, but we hate the disease of alcoholism.
I'm so sorry that you're going through this.
(((((hugs)))))