Attention all Christian paranoids and neo-druids. All Hallows Eve and All Saints Day are Christian holidays. Christians do not have to initiate imitation Halloween celebrations, calling them "harvest festivals" as if the word Halloween was tainted. And Wiccans and the like have no business reclaiming the "true" heritage of the ancient Celts and calling it their day.
So for a moment, set aside the undeniable fact that as Creator, all days (and nights!) really belong to our Father and no one else. This one's all about story. Those who think of Halloween as a devilish holiday think of the Church co-opting pagan holidays in some ineffective and paltry manner to try and woo primitive and medieval societies away from their true heritage. How silly to take the great festival of Samhain and call it All Saints Day. At least that seems be the way it's been told.
Let's try a different story. The Celts had the druids, the real druids. The genuine article. And guess what. When the light of Jesus shone in their culture, they turned to him and rejected them. Their nature-religion-based worldview was uniquely transformed into one of the most beautiful expressions of the Faith ever known. No one who is exposed to even a small part of what they bring can deny the powerful genuineness of their whole culture conversion. And they had the total right to re-purpose whatever holidays they wished. Done deal.