I read this book to my son recently, and I want to recommend it to someone but can't for the life of me remember the author or the title or anything but the vaguest details of the story!
There are two children, a boy who is quite straight laced, and a girl who is more rebellious. She lets off some fireworks at the boy's house at a party. The boy's baby sister (Shilpa) gets stolen by a fairy (Maevis?) who comes through a mirror, and the children follow them to rescue her. They have to complete a series of magical tasks. There's an evil fairy queen who's turning human babies into little goblins.
Anyone?! It was really good!