J.V.
I honestly am not sure why his drinking habit is your business, unless it is directly negatively effecting you, i.e. he is driving you or your kids while drunk, yelling at people, or otherwise engaging in destructive behavior.
Everyone has their vices, and they are theirs to have, unless they effective others negatively. I honestly am appalled at women who strive to be a size zero when they have young daughters at home --weight issues are as serious as drinking issues, if you ask me. But, no one asks me because really it isn't any of my business.
At the end of the day, people do what they need to do to live their lives to the best of their abilities. Unless they want help, there is nothing, and I mean, nothing you can do, save for trying to take away car keys in this case.
Your concern is commendable, but really, he is a big boy and he WILL make his own decisions, no matter what you say or do.