What kind of "support" are you needing from your sisters? Do they not know that you have a drink problem? If you are 62 and still drinking, I'm sure they already know.
I agree with ColdFusion, I would think long and hard about your motivations for disclosing this to them right now. If you are about to be unemployed, there is going to be a lot of uncertainty in your life soon.
Are you still drinking? If so, this is a really important thing to tackle before you find yourself with too much time on your hands and possible anxiety from job loss.