I'm sorry.  Tell me why we are dragging children into adult issues again?  Hallowe'en is a time for fantasy and imagination.  The question usually asked is "So what do you want dress up as for Hallowe'en.  Children's choices are something they like/admire.  Stop reading some kind of twisted malice into their innocence.  It's a "dress up" play day with candy.  Stop micromanaging their thoughts, ideas, creativity, and likes.  Let them be kids.