Melbourne shuffle: Theres a reason it's called that
If I was 18 I'd be going to clubs, Melbourne has (apparently) the best rave scene in australia and is home to the melbourne shuffle (of course) which is a rave dance. We have a very unique dance scene down here which is pretty freaking amazing.

Music that you can only find in europe and other cool stuff
There is loads of places to see and go to, but be warned, melbourne is also the 'city of weather' Be sure to take a rain coat and shorts on the same day, because we go through all four seasons in the period of 2 hours

very fun.
Luna park isn't that great. It's small and..... small I guess you could say (yes, 2x as small as normal luna park) lol. It's also extreemly expensive.
You're from nsw, so i reccomend fitting in a tram trip somewhere along the way

I didn't get to go on your cool double decker trains *annoyed*
Uhhmmm... Philip island is pretty good. Make sure to go to a maze n' things. (awesomly cool amazing things there :p My favourite is the ames room) Penguin parade is alright, bit boring after the first half an hour, but worth it to go see during autumn or spring (summer = mosquitoes. Winter = rain)
Oh, make sure you come down on a weekend when we're doing leafletting, it would be very cool to have more people