When ever I'm asked to be the piano man at an event where there are children, I always accept strait away because of the fun I have, children don't like to go to a serious concert and sit there for over an hour listening.
They like to be a part of it; as soon as I start playing piano, children come from around the room, usually it's one that wants to have a go on the piano, so I'll show him or her a few tunes to play with me.
Then when the others see that happen, they all want to be a part of it so they all take turns playing simple tunes that I show them, and to make things more musical I'll play a nice accompaniment for them.
At the end of the event I'll have people asking me how I got their child to play a tune so fast, and if I teach etc... Well, children and music go together so well. I teach piano, so that's what I've talked about here, even if it's not piano though, you should always try and find away to incorporate music into a child's life.
So with piano, children will usually want to learn, the only thing you have to be careful of is making sure that you don't take that want away by making them practice too much or making them go to a teacher that they don't like, and when you want to inspire them, don't take them to an amazing concert pianist where they have to sit and do nothing but listen, take them to something casual where they can be a part of the action, where they themselves can become the star!!!