Turn him in, he cannot be serious about his job if he wants to turn up smelling of drink. Let him find an alternative career like running a pub.
why should you feel guilty. Afterall its he who has turned up unfit through drink. It is a choice he has made, its not your choice.
If a crew members cannot make the right choice then they have no place being entrusted with peoples lives.
Personally I am in favour of breathtesting when signing in. I dont care either if taxi drivers etc dont have to go through it. They dont have 200 people sitting behind them going through the air at 500mph with millions below.
If you dont like it get another job.