The 'Home' singer's little boy is set to undergo treatment for liver cancer.
Watch Oz: The Great and Powerful trailer
Watch the trailer for Sam Raimi's prequel to 1939 classic The Wizard of Oz, starring James Franco, Mila Kunis, and Rachel Weisz.
The film will tell the tale of Oscar Diggs (Franco), a small-time circus magician who comes across a mystical land and decides to become The Wizard of Oz!
However, Oscar then runs into the three witches, played by Kunis, Williams and Weisz, who are unconvinced by the new wizard.
Thrown into the deep end, Oscar has to decide who is 'good' and who is 'evil' as the Land of Oz is faced with epic problems.
Oz: The Great and Powerful hits cinemas nationwide March 8th 2013. Watch the trailer below:
The star headed straight from the jungle to panto...but clearly hadn't had time to learn her lines!