I don't have a 9 year old, and in my experience their interests vary considerably. When my visiting niece saw an Isaiah Zagar mosaic (maybe you remember our Christmas Card) on a dumpy little wall in our neighborhood she was hooked. A few hours of walking in circles in his Magic Garden didn't cure her addiction. We examined every nook and cranny, and read every word. Who knew something I have been walking past for years would be such a hit. There were disappointingly few kids there during our visit. If your family is headed to PHL this summer, add it to your must see list. The price is so reasonable ($2 for school age kids) you can't lose.
I'm afraid if I don't produce some tile for my niece to shatter and a wall for her to mosaic, she'll consider her trip a sorry waste of time.