Using a computer without having a mouse is a difficult task. If you're looking for a mouse for your child, this one could work very well.
From Amazon
Perixx PERIMICE-201PII B, Wired PS2 Optical Mouse - 3 Button - 1000dpi Resolution - 1.8m Cable - Black
Conrad Electronic
Perixx Perimice-201 Mouse PS2 Optical Black 3 Buttons 1000 dpi