I have bought 2 different packs for my daughter- who was a large-sized 5 when I got the pack, but it a large-sized six now. The first was one of the kathmandu children's packs, and the second is a tatonka daypack (around 12L I think). She exclusively uses the kathmandu pack for bushwalking now. Don't know the Osprey pack, but $60 is alright.
Some observations:
1) THey can only carry around 1-2 kg max for any great distance, and being able to cram volume in the pack is better than weight. Laura usually carries her sleeping bag, a small drinking bottle, a small bag of snacks and Gerald the giraffe. You can also get her a "special hiking friend" who is smaller.
2) Adult daypacks tend to not be good for volume IMHO
3) IMHO if the pack is big enough or heavy enough to require anything other than shoulder straps, it's too big, and can hurt her.
Also, Osprey makes a pretty fancy-looking scaled-down rucksack for kids when she is around 10. Buy from the US and use a re-mailing service, as imported osprey stuff is grossly over-priced.
I've bought a North Face Blue Ridge sleeping bag for my daughter- it'll fit her until she is 5 foot, and in my experience is good to below zero. It weighs around 1 kg. Don't buy a down bag- if they pee in them you've got big problems.
Boots have been our biggest problem. The couple of brands you can get here are just outrageous, and really poor products. We've bought several pairs of waterproof lace-ups from
http://www.llbean.com and been very happy with them. We buy a tad big for her in the winter, when she wears thick socks, and then let her grow into them. Remember US sizes are different to Aussie sizes- measure her feet.
Cheers
All good things are wild, and free.