It is even harder to find suitable clothes and gear for kids than it is for adults. Too often kids clothing and gear is just scaled down crappy stuff, which makes it even more crappy the way it is scaled down. You really have to 'design' for yourself what makes sense, then look for it. Some of it you might be better off making. Because its smaller it is easier to make than adult stuff, so it makes sense that if you should DIY anything it should be for them. Maybe you can do it with them.

Some of the stuff I find most difficult for smaller kids:
1. Running shoes that are not to clunky and high off the ground.
2. Winter boots that they can actually walk and run and play in.
3. Cheap light nylon wind jacket and pants. Most stuff is so heavy by the time you put it on there is not much room left for insulation layers.
4. Rain gear that is not to heavy and cumbersome.
5. Sweaters and hooded sweaters and skin layers that are 100% wool.
6. Daypacks that actually fit and are not too heavy for small preteens.
7. Ultralight backpacks that fit small teenagers.

Fortunately it is possible to find good fleece and synthetic skin layers for kids, but they should mix wool with that. I think the ideal for kids would be a wool skin layer under quality fleece, and a hooded wool sweater if its really cold. There are some good sleeping bags. Make sure most of the weight is insulation. I agree with Dimitri that the smallest children shouldn't carry everything they need. All the more reason that they shouldn't have a 4 pound pack to carry 6 pounds of stuff. My 8 year old daughter now carries a small shoulder slung bag with just the stuff she likes most, like map, compass, whistle, thermometer, noculars, water, snack, her wind layers, her hat and mitts, and a stick. Always a stick. <img src="/forums/images/graemlins/smile.gif" alt="" />