Flights just for the hell of it...timing?

[Jack B]

In about two weeks I'm going to fly down to melbourne and back with my nephew, who lives in Melbourne and has never flown, and I'll be flying straight back to Sydney due work commitments. Expensive little day trip, but I love flying! How many hours do you think would be best to leave between arrival and depature time at MEL to avoid any difficulties?

In addition, are any flights in particular more likely to be operate by 767RRs?