Hello there Jason B--
What a coincidence, I have a 10 year old and took her kayak shopping yesterday. My background is in marathon kayak racing as well as kayak fishing both freshwater and offshore. I fish from a Kaskazi Dorado II and race surf ski kayaks.
We went to West Marine and also Dick's. West Marine had a lot of stuff which was up on the ceiling that she couldn't try out. Most of it was way too long and wide for her.
Dick's was great, because we could pull the yaks off the shelves and sit in them all. The surprising thing was, some of the shorter kayaks (9 feet long) had foot pegs that were set too far in for her to reach with her feet and flex her knees. The best fitting-one we found was this one= the Perception Sport Rythmn 11 feet. It's got a nice seat, back hatch, deck bungie rigging, and the foot pegs zoom all the way up so a smaller child can reach them. As she grows, she'll still be able to use it since when I got in it fit me fine also. Another consideration is the boat has a true bulkhead in the rear, above the back hatch. This is an important safety feature IMHO that I like to see in a kayak. I'm going to pick up this kayak today at Dick's and register it, so she can enter in a race with me on Sunday. Most shorter kayaks are a real beast to paddle, since they don't have a rudder and are notoriously bad at tracking. If you go on any longer trips with your daughter, it might be good to keep this in mind, because she's probably going to get tired keeping up with you in a longer and better tracking kayak.
Be careful about paddles-- She should be able to stand with the paddle and reach the upper blade with her fingertips. If she can't, then the paddle is too long for her.
Good luck to you and your daughter! Kayaking is a fantastic thing to share with family and friends. Keep us posted on what you discover.