Personally, I don't see any harm in dressing up like a cartoon hero or a fairy princess and getting people to give you candy for no apparent reason. Seems rather industrious to me.
However, I do understand the reluctance of some to promote and participate in Halloween festivities -- if only because doing so seems to trivialize and inoculate us against the actual existence of real evil incarnated in the world. So, for those who dislike the "celebration" of Halloween by church people, I have a couple of idea that (in my very humble opinion) beat the "Harvest Celebrations" or "Howl-elluiah" euphemisms for Halloween that many churches try to offer as alternatives.
The first is has historical significance in that it is the commemoration of an event that took place on the very day that Halloween has come to be celebrated. It was on October 31, 1517 that Martin Luther nailed his Ninety-Five Theses to the door of the Castle Church in Wittenberg, Germany, an act that set the Reformation in motion.
If that's not enough (or if you're Catholic and don't appreciate Luther as much as I do), consider this: In the early Christian church it was a practice to solemnize the anniversary of a the death of a martyr. In the fourth century, neighboring church districts began to interchange these memorial feasts and join together in doing so. As the church grew larger it became common for groups of martyrs to be massacred en masse (and especially under the more systematic persecution of the Roman Emperor, Diocletian), this led to joint commemorations. Soon however, the number of martyrs needing to be memorialized became so great that the church decided to establish a common day for all. As early as 411 A.D. there was a "Commemoratio Confessorum" insitutued on the calendar in use at that time for the Friday after Easter. Finally, Pope Gregory III (731-741 A.D.) consecrated a chapel in the Basilica of St. Peter to all the saints, fixed the anniversary for November 1, and named it All Saints Day. (source: New Advent Catholic Encyclopedia)
So there you have it. Two reasons (other than ghosts, witches and the like) to celebrate a real Christian holiday on October 31st ... even if neither will land you any candy.