I'd put a pack right up there with a sleeping bag - maybe ahead of it - for a troop that hikes a lot. I've seen a lot of little kids that become packs-with-legs because their parents buy an adult-size pack that "he'll grow into" - if he doesn't totally lose interest because he totes around too much crap in a pack because it will hold it all, and which doesn't even come close to fitting, with the result that he never learns that a load doesn't have to just hang from his shoulders. REI and (last time I checked) the Boy Scouts both had good-quality kid-specific packs that weren't too hard on the checkbook.