We cruised on the Magic for Halloween. We loved it. A map was left in our stateroom of trick or treat stations along with a bag to trick or treat with. Perhaps 10-12 stations disbursed throughout the ship (I can't remember exact). I believe it was around 4 or 5 pm. The last trick or treat station was at the top deck where there was a dance party.
There was an abundance of candy. The whole thing did not last long. I believe 45 minutes for TOT, and another half hour- 45 minutes for the dance party. We were on Key west that day, so we made sure to be back on the ship by 3 so my kids had enough time to put their costumes on.
The next day all Halloween remnants were gone (window decals, etc.). My kids were very small at the time and LOVED IT!
We love the Holiday cruises, and are doing Thanksgiving this year...