Fish gift exchange

I have family that are wanting to do a cruise with Disney, they have three children and and I was wondering how popular is the fish exchange?

It depends on the specific cruise. We've been on cruises with FE groups of over 100 cabins (this is a mistake--if it gets big, they should split into smaller groups), and some where it seemed to be 10 cabins. Go to their cruise group on a social media site or their roll call on CC to get involved in a group...or don't if they aren't interested in the work and the expense. The kids won't know what they are missing. I did them a few times; not any more. Effort, cost, luggage space, and I don't need to collect a bunch of junk. On the positive side, it is fun to come back to your room and find a "surprise."