It is legal for those aged over 5 to drink on private property (so at someone's house). However, if you're hiring somewhere out, they will be committing a criminal offence by serving those under 18 and anyone who appears to be under 25 without ID. A lot of places do serve anyone regardless as it gets tedious to check for ID every time, especially when some are of age and some aren't. They may be lenient but don't be surprised if they ID and refuse to serve as they risk losing their alcohol license otherwise. Also, they are supposed to stop serving people who they believe to be "too drunk" so even ID doesn't guarantee you service towards the end of the night if you're asking for a 5th vodka shot.
Posted from TSR Mobile