My family doesn't celebrate Halloween. It's a matter of personal conviction that we not celebrate things that seem to not be of God. Every year we re-address the "why not?" and ask ourselves these questions:
What images are associated with Halloween? are those images representative of God?
Does God like us to be afraid?
Can we support one part of Halloween (dressing up, getting candy, etc.) and still be against the evil aspects of it?
Is the celebration of darkness part of God's character?
Will our children regret not getting to trick or treat?
I hope that these quetions have made you think, too. Here is an article that explains the "Why not?" of my convictions. I'd type out a lot of the same info, if I had the time. My prayer is that it can be an encouragement to you, too, to maybe say, "No" to this overly popular day.