A close friend of mine has co-owned a house with her alcoholic sister for 5 years, and my friend decided recently that she is ready to move on.
She has continued living with her alcoholic sister while negotiating the financial issues around the house, and it has been volatile. She hoped to have rational conversations and fair agreements with her sister, but sometimes out of the blue her sister has blindsided her with devastating criticisms--"going for the jugular" is how it is described in some texts--and my friend has been very shaken by this verbal abuse (which is framed by the alcoholic to sound totally rational).
I think it is perhaps a great risk to announce to an alcoholic that great changes are underway, if the alcoholic wants the status quo to continue for whatever reasons--emotional or financial. Because alcoholism is a disease of resentment. And resentments nursed by the alcoholic have a very ugly way of suddenly being let out in the light of day, often when one least expects it.
If I were in your shoes, I would have my ducks very much in a row, and a very tight calendar in my head about when the changes will occur, and plenty of physical support and presence from friends or family. This does not have to be a war. But alcoholics cannot be trusted to be in any way predictable.
I also recommend you find some counseling for your son. I feel that every child of an alcoholic needs some counseling, and most especially during the break-up of his parents' marriage.
Wishing you all the best in your efforts to make a safe life.