Swizzle
I'm new here but I have ordered what I think is the perfect pack. It is a MOLLE style pack. It weighs a mere 1.5 pounds and is the most versatile pack I have ever seen. You can carry any load you want, from you lightweight summer setup, your winter setup, it can carry tools and equipment, it can be stripped down after you have made camp and used to carry firewood back to the camp. The pack is also adjustable. Both the shoulder straps and the hip belt adjust to fit any size torso so as he grows you can adjust the pack to fit him. And I can go on and on about his pack so let me shut-up and post a link to the Molly Mac Pack (MMP) http://www.mollymacpack.com/pack.html.
It's not very pretty but watch Rat's reviews on you tube he gives a very good detailed view of the pack and shows how to build different loads. I don't work for the company but I highly recommend them.