There are some other threads on this, so you may want to check them out.
I did it with my kids last week, and thought it was really cool.
The pros:
1. gets you to go through the countries more thoroughly and see things you might have otherwise missed.
2. interactive things are really cool
The cons: if you're like our family and just breeze through countries as you go along the World Showcase, it will take you more time to go through the countries that have missions. if everyone in your group isn't into it, they might feel like it's time consuming.
As you enter the World Showcase, you can sign up and get phones. You will be asked to help Kim Possible save the world by hunting for bad guys. You'll be given a slip to go to a specific country and pick up your phone and start your mission. The phone gives you all the directions. When you're done, just return the phone to one of the Kim Possible booths.
If you have never been to Epcot's World Showcase, I would definitely recommend it because it takes you through a country.
My kids were 7 and 6 - the 7 year old was into it but the 6 year old only wanted to play with the phone.