if I may contradict in a daring manner, I think a celebration of the macabre does have a place in life. In fact, there are a whole lot of people who think of Christians as being macabre, Orthodox and Catholics in particular. After all, we do traffic in stories of brave men who met an untimely and horrifying death and there are monasteries with catacombs full of skulls. Jonathan Pageau has this great take, that, really, most things that exist as symbols have a place, but only Christ can show you where they are to be placed.
Halloween being tacky and gaudy, I think, is very much an outcome of Pharisee rule over the Western culture, the US in particular. I would have to say the same about Christmas. However, humorously encountering the darker aspects of human spiritual experience is something very worthwhile on a cultural level, and I think it's good when children are familiar with that.
In the absence of Christianity, it runs risk of becoming a fetishization of the horrifying, but confronting the horrifying can otherwise be very beneficial to a Christian life, in my opinion. Actually, what drew me to Orthodoxy among other things was that it seemed to acknowledge the twisted, rotten nature of our spiritual life more head-on than other confessions.
Romania is probably one of the most consistently Orthodox nations in the world, and they actually have a multitude of festivities in each region which include a type of scary dress-up, in one way or another, symbolizing the encounter with the demonic, usually as bears or weird demons.
Whether or not you should let your children partake in such festivities in Western countries is another can of worms. It's probably not even a good idea to let your children go to birthdays or even protestant confirmation celebrations if you are worried about negative sinful influences. I think what's way more important than keeping bad influences away, is maintaining the influence of the Church above all. I am a very sick and corrupted man, and I don't think going trick'r'treating on Halloween did it. The absence of religious education and my parents not being married, more so. Consult a priest about these things, obviously, but I frequently find myself surprised that my priest seems to be less concerned about cultural hygiene than me. Just never allow Christ to get out of the picture I guess.
Now, if you'll excuse me, I have a macabre horror flick to watch.