For illigalities, it depends on where you are. Some states in Australia have the UK laws, which states it is OK to consume alcohol on private property from age 5 (I know, that is a bit young!) but not buy until 18, others say no drinking until 18. So please don't assume this is an illegal party because there is alcohol there. Unless you're in a state where alcohol consumption under 18 is banned (can't remember where this is: I'm sure you girls will though) this is not illegal.

As for turning 18 and getting hammered... I'd hope that I had taught my children well enough without needing alcohol that you don't do that! Yes, so I don't intend waiting until my children turn 18, but I do intend to teach responsible drinking before my children even think about alcohol - you do this by leading by example. DS does not see me drunk. DS has seen Daddy very poorly with a hangover. DS has seen Mummy laugh at Daddy loudly and call him silly when he has a hangover. DS also knows Mummy disapproves of people who wander around the town drunk by the disparaging comments she makes. All of this is teaching him about how to treat alcohol, and will continue to teach him about that.