REI's brand of baby backpack for my 28+ pounder. Borrowed a friends Sherpani to try out during the summer. It was pretty good, but the REI version is super adjustable for the adult which means lots more comfort, esp. for longer walks or afternoons hsing the bigger kids. I have used various Keltys over the years and the best one is the second most expensive -- not the backcountry hiking trip version but the second heftiest. Back when I had only four, I once spent nearly 6 hours with about 30 lbs of kid/gear, by myself with the bigger kids, through a hike, vespers program, dinner in a cafeteria and had only the slightest twinge in my shoulders the next day. That said, IMO the REI pack is at least as comfortable and less than half the money. If money is no object, :D get the most expensive and involved model Kelty has -- then compare it side by side with REI's top of the line. It depends on your shape/little guy's tolerance, but REI gives Kelty a serious run for their money. Pardon the pun. Sherpani is least expensive and really not bad for what you get (pack/bag pieces included in the purchase price, not necessarily so for Kelty and REI). If I had to hike across the Andes hauling a kid and gear? It would be the big ol' Kelty with every last feature available. (Don't know why I'd want to do that, but...) For hikes between 4 and 6 hours, or just walking around a park or the house, the REI has been AWESOME -- it even has a spot for a bladder-type thingy (like Camelbak), and a little shatterproof mirror so I can watch Mr. Drooly-pants. I have the pack that zips off the back for my eldest to carry (full of water, to slow him down to the speed of us commoners), and a diaper bag that clips on and off easily (for extra clothes, etc.), and the hood/rain shield. Plus it's been the most easily modified (mostly in height/length) for my growing SNK who can't walk (yet) but shouldn't have to miss out on family hiking -- he can be fully wrapped in a waterproof and lined blankie and off we go.
HTH -- Post pics of what you get! :D