wow lucky you !!! i spent this last summer in Melbourne, and went to sydney so i'm sure i can give some advice on what to see and where to go.
Melbourne has splendid museum and gardens! you must see the exhibition building, and flinder street station and federation square i think :)
then what are you interested about ? how are you like while on holidays ? what do you wanna see ?
if you need good restaurant info i can also help you :)
Break something old to build something new.