I'm glad you are going to give it a chance! Personally, it is my favorite park for all of the reasons that kids don't usually like it. I can imagine a 3 year old getting bored. I love learning about new things and cultures.
Universe of Energy - I wouldn't take a young child due to the noise and length. It is funny, surprising and long. My favorite attraction
The Seas - I love spending time with the manatees. Watching them eat, learning about their rescue
The Land - Living with the Land is amazing. It is so informative. Hydroponics, Behind the Seeds tour etc.
Spaceship Earth is still a classic ride. Human communication is a fascinating subject.
Innoventions - There are a lot of fun games that are still educational.
The World Showcase. I love talking to the CMs, learning their native tongue, eating the food, enjoying the wine. I could spend days there just strolling around and taking in the architecture.