I went on a 4-night Halloween cruise on the Dream in September. Based on that...
The Halloween cruises in 2021 weren't normal. There was no trick or treating at all. Instead, staterooms with kids in them had bags of candy left on the bed during turndown service on "Halloween". Also, most of the Halloween activities were canceled. There were no ghost stories and no stories about the pumpkin tree. They still did the Nightmare Before Christmas "Scream Along", but it was muted and offered at inconvenient times. The Mousequerade party was moved onto the deck instead of the atrium, but it was smaller and took place at the same time as the nightly show, which happened to be Hocus Pocus.
Usually, "Halloween" is night 2 and pirates are night 3, but this time it was all mixed up. The Halloween drinks of the day were still on night 2, but the rest of the Halloween stuff was on night 3, which overlapped with pirate stuff. The cruise director didn't even really mention Halloween at all. Everyone just kind of pretended that it wasn't happening.
All of that said...
1. I took a similar cruise back in 2019 and it was awesome. I don't know if kids were pushing each other to get candy. Probably, because that's what kids do. But the atmosphere and the extra activities were great!
2. Even on this muted Halloween cruise, there was some fun to be had. For instance, we left our stateroom host a "Happy Halloween" drawing with ghosts and bats and then he made a ghost and a bat from towels and hung them from the curtain rails with hangers! They were fantastic! Our server surprised us with an extra chocolate mousse spider for dessert, too. And, there were also some Halloween-themed desserts available at the cafe. So, it wasn't all bad.