There is the project I build for my two years old son. He like playing with all kinds of buttons he found everywhere. But they almost done nothing for him, except the ones on my dryer. So I decided to give him an box full of buttons that take different action on lights and a motor.
Step 1: Choose components wisely
For my son and for many other kids, it's not only what the buttons do, but how to manipulate them and trigger them. So it's a fairly choice to get different types of buttons like one you swap, some you lift, other you pull or push. So I found about 10 types of buttons from an electronic store nearby.
The actions I planned for the buttons is to trigger some lights and one motor. I have chosen leds for almost all of them except for two, because I wanted the box to work with batteries. I used four C type batteries, so the box works a while with this power source.