I was there for Mother's Day a few years ago(2002), and I was astonished at
how hot it was. I usually go in Dec. so I was unaccustomed to it. It was
high 80's at LEAST. I don't believe it rained. If you like hot, go for it. After
all, it's Florida!
It is hot at WDW in May, but it should be totally different on the cruise at sea. I would post this ? on the cruise line forums. You'll prob get a much better idea.