Have you tried trackball-type mice? They are stationary, so youngsters don't have the frustration of a regular mouse (or the little touchpads on laptops). My DS was able to use my trackball mouse at a very early age. The best one imho (microsoft explorer trackball) is no longer on the market, but there are a bunch on this site to look at, including kid's versions:
http://www.trackballworld.comI am just replacing my MS explorer with a logitech cordless optical trackman, but haven't rec'd it yet, so can't review.
