My 8-year old daughter and I made a piano.
We used followed the piano tutorial, using the Invention touch board, but made piano keys from aluminum HVAC tape from the hardware store. The only change we made to the code was to make the output pin to the piezo speaker to be pin 13, that way the LED on the board lights up when any piano key is pressed.
Using a usb power bank to run the board makes the entire thing portable. Just make sure to use one that doesn’t automatically turn off if it’s a relatively small current draw!
The whole project is so light that we can just put it up on the wall with a bit of double-sided tape. We put it in the hallway partly because there’s an electric outlet right there (with a mini USB power supply) and we can play piano when walking to the bathroom or back bedrooms!