We were on the 9/12 4 night. It was the first HotHS for the Wish, so things could be adapting and changing:
The characters were in their costumes throughout the sailing. Including several opportunities to get photos with the "Sanderson Sisters" (Minnie, Clarabelle and Daisy).
The Lighting of the (GORGEOUS) Halloween tree (named Boo) happened our Second night, and all the Halloween party festivities happened that night as well. The drink of the day that day was the 'Haunted-Rita', and the halloween show "Mickey's Mouseqerade Party" happened after the first showing of The Little Mermaid (So you don't have to miss the show to see the Halloween Party". They had bags of halloween candy on a table and you could go ask for them (they asked if you had any kids with you if you were an unaccompanied adult, but they would begrudgingly give you a bag of candy even if you admitted you were not sailing with kids. This was the opposite of the Dream where they encouraged adults to participate in the treat trail and were extremely generous with the candy.
There were Halloween crafts throughout the sailing. Pirate night was night 3 and lots of people wore their Halloween costumes for a second time.
On the dream a few days later there was an awesome Halloween party just for adults (I think it was called Halloween isn't Just for Kids). Hopefully they'll bring that to the Wish as well before the season is up.
Here's a link to a video that has the Navigator with all the activities for that HotHS Wish sailing: