Thank you all for your comments - they were very helpful. Lucky for me, there was no alcohol abuse in my family and none among my friends. So I don't really have anyone to ask, or personal experience to call upon - except what I read on the internet. The collective life experience and wisdom that you reflected upon my particular specific situation and dilemmas is invaluable.
I understand that what I had in mind was the wrong way to go. I will instead attempt some form of control over the cash - so as not to "enable" the drinking, by trying to choke the funding for it. I still have to figure out how exactly I'm going to do it technically and still have her be able to go the store for the mundane stuff of life.
There is a famous quote by Theodore Hesburgh who said "The most important thing a father can do for his children is to love their mother." In my mind, my worry was about my children growing up and asking me tough questions about how did I let their loved mother fall. I am know becoming aware, that no less of a difficult question is how did I let them stay with her when she is drinking heavily.