This just happened to us this last week. We booked the dessert party, not so much for the desserts as for the time it would save us from not having to stake out a spot. (We were doing all 4 parks in one day so time was a big factor.) Well, while we were eating, there was a remarkable lightning storm above the castle. It was like fireworks!!! Well, when Wishes was supposed to start at 10:00, an announcement was made that they were delayed due to an imminent storm. We waited about 40 minutes, then decided to leave so we could do a few attractions in the park. We did not ask for a refund since I had read that they would not give a refund. Throughout the next hour, they kept announcing that it was delayed. I was so frustrated that Wishes was probably going to be cancelled since it was my 40th birthday and this was one of the things I really wanted to see. Well, 10 minutes before midnight, they announced that they were going to present Wishes. Since so many people had left the park, we were able to view them directly in front of the castle. Best seat in the house, and I didn't even have to stake out a spot! It was amazing! I was just frustrated that I had spent the money for mainly the seat and ended up with a better seat! The desserts were definitely NOT worth the price I paid. But oh well, live and learn.
BTW, if you have crowd issues, I'm not sure I would recommend the dessert party anyway. It was a madhouse in there! Lots of people, small area, everyone attacking the desserts. It made me not even want to leave my table to get seconds. I agree with a previous poster about watching them from the Poly beach. I've done that a few times and love it!