That is what my kids did, there wasn't a thought of demons in any of our minds. It meant candy and dress up, only and a witches costume was only a costume that had nothing to do with demons.
The Lord tells us not to copy the pagans. The Lord used what we do physically to explain the spiritual. Until the Holy Spirit was given to all, the Lord used physical circumcision to explain belonging to the Lord and keeping ourselves separate. Could it possibly be that the Lord looks at Halloween as copying pagans, or as we look at it, as an innocent pleasure for the children?