A beers isnt really harmful. And if its no big deal for your kids to drink one, I.E. you dont actively prevent them trying it, well then they wont be tempted to test the rules by accepting one of a stranger. If you teach them rather that its not too good an idea to take anything off someone they dont know, but that if they really want a beer all that badly they are welcome to it then they hopefully will grow up with a mature attitude towards the stuff. As for smoking... i dont think anyone wants their children to breathe smoke, but its something a lot of people enjoy, maybe because it is a little bit dangerous and so if they do it its really their decision. Our society makes it quite clear what the dangers of smoking are, obviously parents usually do a lot to support this and so i feel the individual should be allowed to decide for themselves. If you demonise, drugs or alchohol it will only make kids want to do it more just as a way to rebel, if you let them make their own choices and their own mistakes, with the help of your advice hopefully they can choose well. But ultimately its their life. Also, if your going to come into contact with these things i think its better to do it comfortably at home.