I can’t seem to find a source that gives me one origin for the whole “trick-or-treating” thing, but I found a bunch of different traditions that I think are awesome.
All over Western Europe people played tricks, thought the spirits played tricks, and went around asking for gifts (sometimes in costume and sometimes not). Celts offered treats to avoid spirits playing tricks and Druids asked for favours in return for protection of the soul. By far, my favourite ancient custom is the Irish or English version of “soul-caking”. You can get the recipe here: http://www.catholicculture.org/culture/liturgicalyear/recipes/view.cfm?id=1378.
Essentially, “soulers” went around and sang their songs without stopping or having much tonal variation in return for cakes that were to honour the memory of the dead. Often “soul papers” with prayers for the deceased would accompany the cakes and then the cakes would be given to the poor who were in need of sustenance. One of the old rhymes goes like this:
Soul! Soul! for an apple or two!
If you have no apples, pears will do.
If you have no pears, money will do.
If you have no money, God bless you!
Honestly, there are so many neat customs around this time of year, I don’t know why you wouldn’t use October as a way to teach your kids about Christian history and Christian beliefs/traditions surrounding death. Parents today seem to be afraid to tackle the tough topics with their kids, but this would be a fun and interesting way to get into a discussion with your kids about your beliefs and keep it light and fun so that they are introduced to the idea without it being terribly scary.
As to the whole costume thing. Yes, originally costumes were used so that the roaming dead would not recognize you as one of the living. However, that’s not the meaning of them now. Costumes now are for the entertainment of the children and to have them dress up and have fun. Children aren’t afraid that ghosts and devils are waiting for them at their neighbours’ homes. They enjoy dressing up as their favourite characters from books, movies, and TV shows. They enjoy seeing the costumes that their friends come up with. They like making their own costumes. If you can allow your children to play dress up, a costume on the day of Halloween shouldn’t be any more threatening than a costume on any other day of the year. They Disney characters Buzz Lightyear and Woody don’t change to become evil parodies of themselves for the holiday afterall. Why should it suddenly be harmful because it’s on that specific day?
Most Americans wouldn’t disallow a Christmas tree because it was possibly originally a pagan fertility symbol. Now, we see it as hope for the new year, whether we celebrate as Christian, secular, or both. Neither of my parents had a problem with the whole Santa thing because Santa was explained as St. Nicholas and gift-giving was explained through his story and the story of St. Basil. Santa became the spirit of Christmas with Christ’s birth as the central idea of Christmas. In my house, my father is not a fan of the Easter Bunny because people forget Christ, but the Easter Bunny was a part of my mother’s traditions. We had discussions on this every year, and while we loved the Easter Bunny, we never put him above Christ. To me, Halloween is the same thing. If you talk about the secular traditions with kids and explain the more important religious ones to them, they’re not dumb. Kids do listen. They will eventually absorb what you want them too and will follow the patterns that you set for them in most cases, so long as you lead by discussion and example, not just by talking at them.