Is Walt Disney World fun?

I'm 13 and I'm going there for a week with my family. I heard from a lot of my friends that it's fun, but kind of childish. They said there are no good roller coasters. I'm all about the fast coasters, so when she said that, I was disappointed. Is that true? And also, is it fun? Just wanted a head's up so when I get there I would kind of get the idea of what it's like.