Height and weight doesn't really matter when talking packs, whats your torso length? You want a long enough frame to be able to get good lift. No real disadvantage to the shorter frame if you get lift.
My advice would be not to push the matter to hard. I have one kid that is and has always been all about shooting with dad and another that couldn't care less. You cant make your kids like what you like, they do or they don't. Just because they don't now doesn't mean they wont later. They may...
I haven't upgraded much of anything the past several years.... about the time I stopped looking at the latest and greatest trendy gear. I'm sure I can improve on something or cut a couple ounces here and there but my set up works just fine for me and if it aint broke, I'm not gonna "fix it".
Doesn't seem that distance makes much difference in crowding any more as there are more and more people willing to go the distance. Once you get past the distance the average backpack hunter is willing to hike in, you start to run into the folks on horse back.
I was reading up on the group that's doing the petition for reintroduction in Colorado. Was really surprised to see that they use the Yellowstone elk heard stats since reintroduction in their literature as an argument for their side.