If a Christian is going to take part in Halloween, their attitude, dress, and most importantly, their behavior should still reflect a redeemed life (Phil 1:27). The decision is ultimately yours to make. I believe God's view on the subject is clear: "Be Holy, as I am Holy" (1Peter 1:16). "God is light and in Him is no darkness at all" (I John 1:5b).
Abraham was a hundred years old when his son Isaac was born to him. Sarah said, "God has brought me laughter and everyone who hears about this will laugh with me." - Genesis 21:5-6