I had my 21st at the Sorrento/Duncraig Football Club Rooms. Was a good venue, plenty of inside space, plenty of outdoor space, large oval if u wanna have a kick of the footy in the dark... Was good value for money. Just hired a Jukebox for music but the club room's included use of the Kitchen/Ovens and Table's and Chair's.
Just pick a local clubroom near your place, makes it easy when carting all the goods to the clubrooms... Just don't pick one's that have a potential to get gate crashed... ie: Balga club rooms or anywhere in Girrawheen.