aDLFJASLDKFJ EPCOT's my favorite park!
Okay, to start. If your brother is tall enough, check out Mission: Space Green (Less Intense) side. Do the orange for yourself if you're a thrill seeker. (Green side is a lot like Star Tours.) Also do Test Track. Hit Soarin' while you're at it.
My favorite part of EPCOT is World Showcase, which actually bothered me a lot as a kid. There are SO many shops in each country, I could spend forever and a day there. So, shopping = must do for you. However, in various countries (check out the times) there are character greetings. Also, there's a thing called KidCot. Basically, you can decorate your own mask and walk around to each of the countries to get a little "charm" put on it. That's for your brother's entertainment, but it doesn't matter if you do it too.
... I still do KidCot