Sandra,
You can buy insurance to protect against an unexpected cancelation of you plans including about $5.00 per point in point costs, airline fares and related costs. The information is included with the officail Disney confirmation you will receive after you have made your reservation.
Although you are obligated for the points after the reservation has been made and paid for, I usually allow an additional 6 months use from the date you are scheduled to check in if you must cancel for any reason. Keep in mind that is you cancel on the day you are scheduled to check in, the points are lost If you cancel within 30 days of your check in date, you will still have an additional 6 months to use the points but you will only be able to make your new reservation 60 days in advance. Of course, any substitute reservations are subject to availability.