I apologize for extending a thread hijack, but hopefully this will be useful to somebody. If anybody is interested in more, maybe they could start a kid-packing thread…
My son and I hiked most weekends in Hawaii from when he was one year old. One of the most important things I did once he was old enough to start walking on his own was to rope him up. Most of the official trails in the Olympic mountains are tame, but I can remember a few areas where I would definitely have held his hand. In Hawaii, hairy trails are the norm. Even on some of the highly traveled trails it's typical to have a two-foot-wide trail and a 30-foot drop onto rocks in a streambed. It doesn't take more than a butterfly for a kid to walk right off the edge. Holding a kid's hand for a several miles of rough trail gets tiresome and painful for both.
I bought a Petzl Ouistiti childrens climbing harness, and we fit it to the kid and bar-tacked the heck out of it. We used a locking biner to join the front tie-in loops and instead tied into the back (no sense jerking the kid around in a half-circle on every fall). Along with 15 feet of climbing webbing and another couple of locking biners, the total weight was 26.1 ounces. He was clipped into my Conterra Assault/Rescue Belt (8.4 oz) in case I dropped the leash, which I usually held coiled in my hand or in my biner on safe sections of trail. This allowed him to hike safely regardless of hazard, and since he loves to climb he could do so because I had him top-roped. When he was just starting to walk he would fall often, of course, so I held light tension on the leash so when he fell he just dangled instead of skinning his hands and knees. This made hiking much more fun for both of us.
Left: my daughter enduring the obligatory harness test. Right: a five-year-old friend 'hiking'.

