Peripherals/Child Friendly Mouse
Many young children don’t have fully developed motor skills (fine motor skills in the hand and fingers typically develop fully between the ages of 5 and 6) and often have trouble using traditional mouse buttons. Children of this age often click next to targets, find pressing down unintuitive, and grip all their fingers at the same time so that the mouse is squeezed rather than clicked. This can lead to frustration and detract from the educational experience.
This document describes one possible solution. Besides being small, it has a single wide soft button under the front.
I've found that the one button apple mice are intuitive and easy to use for my 3 year old daughter. One simply has to press down on the mouse to click. She can use this mouse where all others were not usable.