I have a 15yo DD and two young sons. We have allowed our DD and older son to have a sip of our wine at the table but they haven't ever asked for it since their original query (we made no fuss, just said that it was an adult drink and they probably wouldn't like it... they didn't!). Recently i have read articles which outline the damage alcohol can do to developing brains and I'm relieved that DD shows (of her own accord) absolutely no interest in drinking it. Now she is in boarding school and i can't imagine her sneaking it in there.... but who knows. I do know that when we were having issues with her behaviour I was closely monitoring our bottle levels and was relieved to observed that they weren't going down or disappearing... they are in easy access in the pantry.
Anyhow I have had a bit of a change of heart over the past year or so. If my youngest now asks for a sip of wine i now say "no, it's only for mummys and daddies". He doesn't ask anymore and seems accepting of that. So yes, i'll be limiting their consumption until they are about 18. I certainly wont be buying it for them and i hear that my DD has been drinking (before 18) rest assured i will be expressing my disappointment.
At the end of the day though i notice a correlation between the drinking habits of parents and their children when they grow up. Drinkers seem to produce drinkers. DH and i are fairly light drinkers. I limit myself to 1 glass a few times a week while cooking meals... and even when i go out for a 'big' night will only have about 3 over the course of 4 - 5 hours. DH is much the same... he will only have a few beers a week... and only sip from my glass, actually say "no, don't bother pouring one for me, i'll just have a sip or two from yours". So my kids don't see us drink heavily.... we certainly model the ability to just have 1... and to enjoy it because of what it is.... not because we feel that that is the social expectation to drink... i think THAT'S what causes problems when kids grow up to think that you drink to 'relax' or to "be sociable". DH has never been the kind of person to come home from work and say things like "Geeze fetch me a beer love, i've had a hell of a day and really need a drink!"

