Back in 2012 my then 5-year old daughter and I recorded and tracked what was probably the first iPi Mocap test done with a small child using two 'old style' XBox Kinect sensors. Back then, the iPi system was not designed for children. For example, the tracking rig could only be scaled down to 1 meter and you could not adjust the body proportions. All things considered, it worked remarkably well:
Mocap Test with Small Child (1 meter tall)Sorry I don't have a more recent 'child mocap' example to show but the current system is much more accurate these days since the body proportions are now customizeable and you can use more and better sensors and cameras.
From what I recall, the trickiest thing was that my daughter moved very quickly and unpredictably, so you may want to consider PS Eye if you have the space and proper lighting for it. However, if you're using PS Eye, the kids will need appropriately colored and properly fitted clothing, which may complicate things.
If you're okay with the lower framerate, the Kinect based system is obviously fine though. TBH, when we recorded this session, I thought it was going to be untrackable, but her little dance actually tracked with reasonable accuracy and minimal clean up. And I was using a beta release of version 2.0 at the time! :)
The other thing to consider is that children at that age do not have a long attention span, so plan your session very carefully so you can keep it flowing briskly and efficiently. Make sure there are things for the kids to do in between recording--if they get bored, you will not be able to get a good performance.
