Did you get the note?
Did you call Disney? You're probably out of luck with them, but maybe they can move it for a change fee (rather than cancelation fee)?
Did you contact the airlines?
I tried dealing with Travel Insured in the spring and there was so much paperwork, but I didn't have a note from a doctor (trip interruption rather than cancelation since it happened in the middle of one of the trips we were on) and we also had "insurance" through the credit card. It wasn't that much money but it was so much paperwork that I just gave up