Bushwalk Australia

I'm looking to kit out my junior hiker for the next few years of adventures, so the first thing needed is a pack. I'm very much weight conscious, so keeping that low is key - beyond that his waist measurement (or lack thereof) is a deciding factor.

Possible options:
Osprey Jet 18
Deuter Climber
Deuter Fox 30
Macpac Torlesse Jr
Decathlon MH500 18L
Decathlon MH500 30L
Gregory Icarus 30

Avoiding for now:
Osprey Ace 38 (too heavy and unnecessary capacity)