Plot (what I can remember):
There are two sisters, who I believe in the opening scene are in the back seat of a car going someplace with their family. I don't remember exactly what happens, but I have a feeling that the younger girl falls asleep and that the rest of the movie is her dream.

Next thing I remember, the two sisters are on their own in this dream-like world, and, the older sister at least, can wish for whatever she wants and it will show up in front of her. I seem to remember that the younger sister doesn't have this power, no matter how hard she wishes for even the simplest of things, like a glass of water.

I believe there is also a magic man with a wand and a tornado near the end of the movie to defeat an enemy but I can't remember much else.
Thanks :)