You never know what you are going to get. We were there that same week last year and there was not a drop of rain. It was hot- we would have welcomed the chance to get wet and cool off a little. We were also there last December and it poured all day one day, and a good part of the day the next. It wasn't exactly warm, but my DD still loved it. She had a blast running around in the rain and stomping in puddles. The ponchos are great. They will keep most of the kid dry. In May your kids should be in shorts so you don't have to worry about the bottom of their pants legs getting soaked(our biggest December problem). Be sure the kids (and you) have at least 2 pairs of park shoes so if one pair gets soaked they can wear something else the next day. My DD had some mesh tennis shoes for summer that she doesn't wear socks with that dry out pretty quickly. That would be a good option. If the kids are prone to blisters and aren't going to be wearing socks, you may want to put body glide on their feet to prevent blisters. Your kids aren't going to care much whether they are running around in wet tennis shoes anyway. They are just going to be happy they are at WDW. My DD's shoes and socks were soaked in December and she didn't care. Eventually, I made her go back to the resort and change them out because it was pretty cold. (All our shoes and socks were soaked, it was like a monsoon out there!) Had it been warm weather, I would have just let her keep going.