There are four people to interact with, and they mostly stay put in the one place. Sometimes they wander off, and when that happens, have fun snooping through their stuff! (Don't try this at home, kids ... )
Xenia Doukas, the director who plays Persephone, is usually in her box in the audience area of the amphitheater.
Hint 3
Niobe Papadaki, the artist who plays Demeter, is usually in the museum. After you follow her (which happens in the middle of the game), you'll find her in the Workshop sometimes.