Our 4.5 yr old DD just took the cruise on 1/26. Despite cold she loved it. They go out on a pontoon style boat, modified with bench seats, and cover if needed. She was nervous, but once we found another girl for her to buddy up with it was great. The staff that ran it is very organized and upbeat. One staff member during the cruise pretends to try and steal it the treasure, which really gets the kids going. This is a no parent cruise. The kids get to keep some of the loot, mainly trinkets that wouldn't mean much to parents, but are the world to the kids. (Plastic mini-telescopes, rings, plastic lizards, necklace, gooey fake eyeballs, etc).
What we liked about the cruise is it was a non-park event, fairly small number of kids, and for a price much less than taking the family to a character breakfast you get a big memory. DD memory of the breakfasts run together, but the pirate cruise stands out.