Disney's regular cancellation policy (with no insurance plan) is great, so just think about whether you need to purchase one at all. For your room, dining plan, and tickets, I believe they will give you a full refund up to almost a week before your trip, then after that I believe the worst case scenario is a one night room charge but they will let you move your reservation to another date in the future with no charge. Call them to double check the specifics, but unless you are worried about plane tickets, their regular cancellation policy is very lenient.