This is exactly why my grandson is still unaware that we have a trip planned for the end of this month. It's not 100% that we will go and even in the weeks we have had the reservation, things have changed tremendously. After the disappointment he went through when our trip was cancelled 2 days before it was to have started, we do not want him feeling that way again. It took months for him to even stay in the room if the subject of Disney was brought up. So I completely understand the feeling of disappointment that comes with cancelling a long anticipated visits. Been there, done that, too many times.
Please, please take the time to email Disney and tell them your story and your decision. It may not help for this trip, but they need to know what their guests are thinking. I already wrote them and at least they know how this guest feels.