In order to get one of the Year of a Million Dreams lanyard with the two pins on it, you just have to be at the right place at the right time. They have the dream squad, that gets notified on where and when to hand out the Year of a Million Dream prizes. So there is no way for the guests to know, where the Dream squad will be and what they are giving away. So don't feel bad if can't get your hands on one, lot's of people don't get anything from the Dream squad. But who knows you could get lucky!
Just in case though, if you go to Downtown Disney they have a huge pin store there where you can buy lanyard sets or you can buy a lanyard by itself and buy what pins you want to put on it! They should have a lanyard there, that has the year on it( 2008), which would be a real good one to get for your son( so he can remember what year he was there~for his first trip! That's where I buy most all of my Disney pins from, they have the most to pick from! Also at the pin store at Downtown Disney and through out Disney World, you can do pin trading with the Cast Members( just look for Cast Members, wearing a lanyard). The Cast Members have to trade with you. Your son might get a kick out of doing that too!
I hope you guy's have a wonderful first trip to Disney World!!!! And that your son has an awesome 8th birthday at Disney World too! I know you all will have a Blast!!!!!! Be sure to stop at Guest Services before going into the Magic Kingdom, so you all can get a button that says "My first trip to Disney World" and a "It's my birthday" button for your son!