-- Last Updated: Feb-04-13 4:09 PM EST --
The most common problem I see is kids in kayaks that are much too big for them.
Most kids are quick learners, have good reflexes and balance, and are not afraid of getting wet. They want to go fast. Parents are often far more worried about stability than the kids are. A boat that's too wide and/or too deep for a small paddler will be uncomfortable and slow.
SOTs have the advantage of not having to be emptied, but they're usually slower than sit-insides. if you want to paddle with your child that may be a consideration.
Possibilities might include:
WS Tsunami SP
Perception Prodigy XS
Perception Carolina 12 XS/Umiak (discontinued)
Perception Acadia Scout(discontinued)
WS Piccolo (discontinued)
Jackson Mini Tripper
There are also build-your-own options, such as...
A skin-on-frame: http://www.yostwerks.com/SeaFlea1.html
Stitch & glue: http://www.pygmyboats.com/boats/osprey-13-kayak-kit.html