We took our daughter last week on our 7 night cruise. They did it on both of the days at sea - so I don't think they will have it on your 3 night cruise.
Personally though, I don't think you're missing much. The (iced) tea/cookies are already on the table when you get there. Wendy tells a 10 minute story. Then everyone lines up to get a picture with Wendy. And to think, there was a massive line to get tickets for it - and lots of people who didn't get there early enough didn't get tickets. You had to get the tickets on Sunday for Monday/Thursday.