If instead of Halloween it was called Hitler day. Would you still give out treats? And don’t worry it doesn’t really have anything to do with the nazis. that was a long time ago its just a fun things kids do today that has nothing to do with anything.
Just because goyim are happy we do something doesn’t make it a kiddus Hashem. I’m sure they would be happy to if we all converted CV.
How about on Rosh Hashanah give them an apple an honey and wish them a sweet (real) new year.