Shh! Don't tell the kids, but Epcot is.... educational. That's right, it's education masking as fun. There are of course rides, such as Test Track, Mission: Space, and Soarin'. But all of these come with an educational component. I'm sure some people aren't buying this, but I'll explain myself.
When you first get into Epcot, you see the giant golf ball, also known as Spaceship Earth. This ride gives you a trip through the development of communication from cave wall drawings to the advent of the computer to the potential future (with a new surprise visit from you.) When you leave the ride, you get a chance to play games... all with educational components. My daughter loves the game that uses sticks to push energy around to the areas that need it.
A great area for kids to learn in is Innoventions. This is split into two different buildings. Some of the fun, yet informative, things you can do here is make a virtual robot then build your own plastic one to take home (for free!), make a piece of paper from pulp, or learn important fire safety tips.
The Land has a great ride that brings you through a greenhouse using some new growing techniques. The Living Seas not only has Turtle Talk with Crush and the Nemo and friends ride, it has a wonderful aquarium. Journey Into the Imagination is a fun area where you can learn about the sense and creativity. On the other side of the park is Future World. You can learn how they test cars and even take a test run yourself at Test Track. This is a favorite of my family. Mission: Space now has a regular and wimpy version of the ride, but I won't try either. I heard this simulator is very similar to the real ones NASA uses, so we avoid that one.
All this to do and learn, and we haven't even made it to the World Showcase. This area is made up of many different countries. We like to go to each country checking out the stores, eating the food, and talking to the natives who work there. My daughter makes a mask and has the workers at the kids area stamp it. She also likes to ask them a bit about where they're from and their language. I just like trying all the different foods, like Morocco, France, and Germany.
My only warning about Epcot is that it is huge. There's so much to do and so much space to cover, this really can't be done in one day.