Hi there, Elizabeth!
Phineas and Ferb: Agent P's World Showcase Adventure at Epcot is a virtual chase around several pavilion in world Showcase. Each team receives a phone, which uses recorded clues to direct the players around the pavilions to find special, secret information.
If there are telephones available - and they are returned and dispensed constantly throughout the day, as no adventure is more than 45 minutes long - the attraction should be working (pending technical difficulties, of course!).
For children ages 8-11, you might want to seek out the live entertainment, which is typically interactive and lots of fun. Each of the pavilions in World Showcase offers something; grab a Times Guide when you arrive for details.
Have a happy new year - and a wonderful trip!
See you later, celebrator,
-Deborah B.