Hi - told my two sons about AH's alcohol problem about 1 month ago - was very hard and got no help from him that's for sure...
I did this alone - although all of the "experts" say parents should tell kids together about this kind of stuff - I can never predict his behavior and it just seemed like it would be saner.
If your kids are 13 and 19, they already know what's going on. My 7 year old was kind of clueless (except to say "Dad smells like beer sometimes") but the 10 year old was totally up to speed - all of the info I gave him came as no surprise. And my AH isn't one of those loud belligerent physically abusive drunks - he's just constantly on a low simmer to get wasted slowly but surely every weekend.
So I'd almost guarantee that your older kids are aware and that it would be a huge relief to finally hear somebody confirm to them what they already know. Having one parent pretend everything is hunky-dory while the other one is freaking out (whether due to drugs, booze, mental illness, etc) will make kids doubt their instincts about people their entire lives. They'll stop listening to their gut when they get bad vibes from people. I think in part that's why ACOA go on to marry spouses with problems - their internal bullsh** meter has been thrown out of whack by a childhood full of mixed messages.
You are sooooo doing the right thing - it is scary and overwhelming to leave behind what you had imagined your whole life would be. But you are obviously a strong person because you have come this far and decided you and your kids deserve a better life. You Go Girl!!!