Why dont you try trackball?
I got a M305 (Logitech) for my daughter (4 years old) and I ended up ditching my old heavy MS mouse, and now use M305s exclusively. They are light since they are single battery, have an on off switch, and have a small reciever (along with a place inside the mouse to store the reciever).
Plus you can find them on sale regularly for less than $20.![]()