You can buy the passport at any of the coutries around the world showcase. They look just like a leather passport. Its really cool, has stamps for the child to add to each country and a place for a CM in each country to autograph and also stamp. In our experience the CM's write a personal note to the child by name or about their fav thing in their country. You can also stop at the "kidspot" at each country and make a mask - this is free vs the 12.00 for the passport. The mast can be colored and or decorated and each country stamps the stick and gives the child somethem particular to that country to add to the mask. Both activites are really great - probably the 3-9yo would enjoy the mask and then say 6 and up would enjoy the passport instead or as well as the mask!! My girls are 6 and 8 and have done the mask every year for the past 4, this was the first year we did the passports and they both liked them but my 8yo was much more into the passport and my 6yo liked the mask better.
You didn't mention the ages of your children but my girls LOVE epcot, especially the world showcase. They really enjoy all the live entertainment and I think they find it refreshing after a day of rides at MK or MGM. They espcially like the acrobats at China and the mask show in Italy as well as the living statue, don't miss the candy maker in Japan or any of the singers in the American Pavilion. My girls love American Vibe while I perfer Voices of Liberty but we all like them both. Off Kilter is another of our family favorites.
OK - sorry more info than you requested, HTH
TJ