When you do finally tell them, it probably will not be a big thing.
When I came out as an addict to my friends, we started going out to coffee shops instead of bars, and there were a lot more non-alcoholic beverages at parties in their homes.
I finally had to tell them that I was okay if they drank in front of me or wanted to go to a bar. But I was really touched that they wanted to help me.
Drinking is not as big a deal for most people as it is for us.