I am so sorry that you're going thru this. To be honest, when I go to Al-anon meetings, the stories that break my heart the most are the ones from the couple of dads there. It is beyond my wildest imagination how a mother can become an alcoholic, and not do everything to correct the situation so as to be able to mother her children. I cry everytime these men speak. Absolutely heart-breaking.
First...has your wife been treated for depression and/or anxiety issues? It's very likely that she suffers from one/both and uses alcohol to cope.
Secondly...I wouldn't let her back into the home until she "gets it" and is SOBER for a convincing amount of time. However, since the little ones want/love their mommy, I would try to work out some kind of supervised situation (even if you're the supervisor) so that they can see her in a HEALTHY setting on a regular basis. You need to minimize the damage to your most precious children.