I'll just chime in on the topic of physical limitations by noting that practicing an instrument when your body is not sized correctly or strong enough for the instrument can create bad habits, and even injury.

At that age, we listened to lots of recordings and live concerts, we played for them so they could see proper technique (piano, in this case), and we sang or played rhythm instruments together. And make sure any instruments you have around the house are in tune, because there are few things more painful for a musical child than having perfect pitch tuned to the wrong reference pitches.

...pronounced like the long vowel and first letter of the alphabet...