Priceline does have a policy of accommodating customers when a flight is cancelled, check their web site for details. Typically the accommodation is in the form of transportation on the next flight (excluding sold out flights).
However the general rule is that anyone who sells goods or services and the goods or services as described are not delivered, is liable for refunding the customer's money. If worst comes to worst you may take that attitude and dispute the charge on your credit card. The airlines are not entitled to keep the revenue for prepaid seats (what Priceline arranges) on flights that are not flown and for which replacement flights usable by the customers or customers' assignees are not rendered.
You might get a refund if the airlines are shut down for so long that the next available flight is after your vacation time is over, this is something you should ask about.
You are not automatically entitled to a refund if you choose not to fly because you are suddenly afraid of flying. You are not automatically entitled to a refund because the replacement flight is on an airline you don't like.
You should get the rest of your rental car period or the rest of your hotel room stay if you get there late due to flight problems, but no automatic refund and no guaranteed extension of days. Some hotels and car rental agencies will cancel prepaid reservations with a full refund.
More Disney tips:
http://members.aol.com/ajaynejr/disney.htm
9/65
Disneyland
3/75 (World Inn* off I4 near DD)
4/85 (Kon-Tiki* on 192)
'80s Disneyland once or twice
7/94 PORiv
9/97 ASMu
11/98 ASMu
12/98 (Knights Inn on 192)
9/99 ASMo
12/00 ASSp
9/01 ASSp
11/01 ASSp planned
*no longer exists
