You should definitely ask the organizer how they're running it. Usually, one person is the organizer and if there are, say, 50 families participating - they break that down into smaller groups. Most seem to be 10, 15 families per group. Some people will join more than one group b/c they really love it. I suspect those people are far craftier than me! But you'd never have to exchange with a really larger number of families.
If it's "worth it" totally depends on your kids. My eldest (who is now 12 but was 11 when we did it, and a girl) LOVED it and can't wait to do it again. She loved checking the fish extender for surprises, she loved delivering them, she loved seeing all the fish extenders, just the whole thing made her
DCL experience more fun. My youngest (8yo boy) - completely indifferent. He didn't come with us to deliver, and he wasn't that interested in checking ours for gifts. In retrospect, this makes complete sense with these 2. Unless people are dropping video games and Roblox gift cards into that fish extender, he's not likely to be all that interested! Whereas my daughter is a huge Disney fan and will be charmed by nearly anything she gets. I thought he'd be more into it than he was just b/c of his age, but nope. I think he would have enjoyed it more a few years ago. But I think my daughter will always enjoy it! For our next cruise, I'll turn it into a mother/daughter project to prolong her fun. And maybe, er, capitalize on my daughter being far craftier than me.

So worth is completely dependent on your kiddos.