The theme of 'Dragonwings' is change. People are usually worried about change, but the change most likely will have a positibe outcome, which is what happens with Moon Shadow and his family. The setting in the book first took place in China, which was Moon Shadow's first home.
Here's an example: Nearly every characteristic presented in the play has an opposite: Helena is tall, Hermia is short; Puck plays pranks, Bottom is the victim of pranks; Titania is beautiful, Bottom is grotesque. I hope this helps.