Guardian Ad Litem
GAL is a person appointed by the courts for the children. He/she investigates both sides, talks to kids, parents, grandparents, schools, and anyone involved. They are supposed to be unbiased...(in my custody case, this wasn't true, won't bore you about that)....and then they make a recommendation to the court on who should get custody and why. The courts almost 99% of the time, follow whatever the GAL says. The GAL should be able to find out if your ex is an alcoholic or not....and I say "should" because we all know how well the A's are at hiding it from the outside world.
To get a GAL appointed, just have your attorney file a motion to request it. Expect to pay out your nose for him/her, but if you can afford it, it is an option that will benefit the kids. The courts go on and on about the "best interest of the children", but sometimes its the "best amount of money they can get". Sad, but very true.
Good luck....it will all work out.