Steve, I want to comment further on your post. I was "that wife." I didn't have the abuse or neglect outright as a child but the alcoholism runs in my family and I witnessed a lot as a child.
My husband and I got to the point you are at right now with your wife. My husband tried to talk to me, told my doctor (I switched doctors), etc. I didn't do anything about my problem until he took action on his own for HIMSELF. My husband told me, "I will not allow alcohol in the house any longer and I will be attending weekly Alanon meetings." I was like, wow he really cares about me and our relationship, he is going to get his own help!!!! So that night I went to an AA meeting.
I'm not saying your wife will respond as quickly as I did but what I think will eventually happen is she will see you detaching with love and taking care of yourself. Once she sees this she will realize you mean business. Your son deserves this from you. He is young and doesn't yet have a voice or the ability to take action. You have to do this on behalf of your son.
Your wife is most likely evaluating her situation even though she's not letting you in on it. I bet you anything she is feeling pretty badly about herself. I can also bet that even though she is working and maintaining a level of responsibility she is suffering physically as well.
Separete yourself from her emotionally and don't engage in ANY discussion of drinking with her. Go to meetings - kids can go and play while you talk. Your son will start to know what's up pretty soon so the quicker you can get yourself support the better.
Since I was the wife in this sinario please let me know if you have any questions and I will try to help if I can in a small way.