I think your daughter's situation is totally different at 10 though. I'm assuming this cruise was a special occasion for your family and not your 6th or so cruise that year. I also think at 10, she's capable of understanding that she's missing Trick or Treat but she doing all these other really cool things that the ship has to offer.Not defending them at all, but we went on the first season of the Halloween on the High Seas over Oct 31 and it was really well done. There were multiple nights of activities, the character costumes were fun (no Sanderson sisters then), and all the guests went all out with their costumes. My daughter was around 10 at the time and thought she might miss "real" trick or treating and once we were there didn't miss a thing. Probably one of the best Halloweens we've ever had.
J$ is not going to experience anything past 7pm on that cruise. They don't take him the show. They don't take him to the deck party. Last year, the British couple came over and they did a little Trick or Treating, but J$ was just about to turn 2. This year, at almost 3, would/could be his very first year truly understanding it and enjoying it. Instead, he'll be in bed because no doubt his parents will want to do some thing that J$ would enjoy without him. They'll meet some characters and go to trivia and have a grand time for sure.