I voted "switch to Autumn decor only" which may be unpopular, but let me elaborate.
I taught kindergarten/1st grade for many years and ALWAYS had a child or two that didn't celebrate various holidays. It was easy enough to make them generic. For art we did Fall leaves, spiders, bats, popcorn, pumpkins, and even monsters, etc. (I'd pick a book that wasn't Halloween themed for monsters like "Where the Wild Things Are.") We could talk about costumes and candy and make it about "some people like to celebrate this holiday at this time of year" so I thought it would be fun to make monsters rather than "we are celebrating Halloween." If a child liked to read/write/draw about witches etc. that was absolutely fine, I just didn't talk much about it other than in the "these are Holidays some people celebrate on this date." I think being inclusive is very important. I chose books to read aloud that focused on Harvest and Fall themes, but kept plenty of fun Halloween books available for free reading time. If I knew a child was not allowed to celebrate the holiday I was more careful than if I had no children in my classroom who had that issue, but why would any teacher want to exclude one of their students? If parties were allowed, those were pretty specific, so I called the parents and we made a plan. Some kept their kids home, some wanted them to go to the schoolwide alternative movie that was provided, some wanted to know specifics and decide accordingly. I made sure to check in with the children and recognize that many kids in the room celebrated Halloween and to let me know if they feel uncomfortable in any way. Most parents want their kids to learn how to navigate their differences so learning how to do so is important.
Doing math with m and m's as manipulatives is not Halloween, doing harvest activities like making applesauce, etc. is not Halloween, writing seasonal stories where some kids might choose to write about Halloween is not endorsing Halloween. I've never particularly liked Halloween (I dislike dressing up in costumes) so I've always empathized with those kids who want to be a part of things but for whatever reason are uncomfortable, but it's also silly to avoid it altogether because many people love it.
I found a phone call home to discuss it with any parent who had let me know of Holiday issues was appreciated and usually they had no problem since they knew I was making an effort not to put their child in a compromising position.