Here is the official policy which I am copying from the back of my families Polynesian room only confirmation.
CANCELLATION POLICY: In order to recieve a refund of your deposit, including credit card desposit transactions, notification of a cancellation must be received 5 days prior to your arrival date. To cancel a reservation, call (407)-W-DISNEY(934-7639), Additionally, if you are holding any other reservations, they will not be cancelled unless you advise us. The cancellation and refund policy are subject to change.