I want them to learn a useful skill, such as playing piano, while they're playing games.
Using Flash and reading in input from a Midi keyboard, I've set up a game that requires to press real piano keys in the sequence and also teaches you how to read music.
The game requires a MIDI controller keyboard, such as M-Audio Oxygen 8.
The keyboard is hooked up to a Max/MSP patch, which reads in MIDI data and generates tones from this data. The patch is available for download here.
There is a Flashserver external which allows for seamless Max/MSP to Flash communication, as Flash does not support MIDI format.
And finally, there is the Flash game itself. You can download the FLA and the AS files here.
You can also see the non-interactive demo here.