Word Of God says that all of the air nomads were also airbenders. (Insert handwavey thing about 'spiritual connection' in the culture, apparently.) So I can totally see society being this sort of overlap of uber-flexible adult behavior, and fairly regimented--if, by all appearances, happy and not overly strict--child-rearing/training. And, on a practical level, if your culture migrates by air... Even with air bison, you want to make sure that all the kids are old enough and competent enough to handle "Whoops, fell off my bison"--or, for that, "whoops, that shipment we're trading just fell off"--fairly adeptly before you send 'em off in the convoys.