I've used them, but not for a Disney hotel. YOu will have to look through your specific offer to see what the cancel policies are; I'm sure they will have links all over, letting you know what the policies are.
Also check with hotels.com. I've been booking DH's business travel through them (and clicking through the rewards site I do to get bonus money!) and have found some nice deals. Hotels.com can be cancelled inside of a certain time period before checking in, but each hotel is different, so with T or Ex, check the exact situation for the exact policies on what you are (exactly) booking!