Joseph,
Giving candies on Halloween is much worse than giving gifts on Christmas as giving Christmas gifts is prohibited only derabanan because of the oved avoda zara may thank his maker (see, Moed Kuttun 9b) while giving candies on Halloween is actually participating in the ritual of avoda zara which is tantamount r”l to Avoduso Darko Bekakh. See Sanhedrin 63a