Spring is indeed risky. For one thing, the months of March and April are the "rainy season", which simply means you have a higher likelihood of days with actual rain as opposed to the standard afternoon thunderstorms.

But the bigger challenge is indeed Spring Break. Besides the families, Disney World has actually become the #1 college Spring Break destination in the world. That fills up at least the cheaper hotel rooms, and you will find pretty long lines in the parks. Pleasure Island can be a blast, though!