That is what I currently do. One thing is good, I can ALWAYS tell he has been drinking even just by how he holds his hands and how he speaks. Even just 1 beer. So on the days he picks up my DD from school, I make him call me on the way there so I know. And no, I do not allow him to drive my kids at all unless I know. So I do not allow him to drive my DD to cheer practice b/c even though I may have known on the way there he was sober, what is he going to do while he waits for her for an hour? I dont know so I don't all it. I truly mean their safety is my #1. Years ago my neighbors had a depressed son who they did not believe if they went out for a little while he would do anything even though he was in a bad place in his life. They left to go to the store and he killed himself in that 15 mins they were gone. They never forgave themselves (although they clearly were not at fault). If something happened to my kids and I could have for one second prevented it I would never forgive myself. Maybe that is not rational but they are what I cherish the very most in life.
Maybe all of you strong people who have left have it all figured out, but unfortunately for me, I don't have that figured out yet. I don't trust the system AT ALL.