In almost 30 years of an IFB old school church I've never heard a message on it, nor participation in it called sin. We've had Trunk or Treat, Fall Festivals, etc, but as far as the dress up thing for our church families and bus-kids we've asked that their costumes be appropriate. Meaning, no immodest or suggestive stuff, and no association with the macabre and/or death.
Having said that, we allowed ALAYBOY to dress up as Mario, Pikachu, a baseball player, etc and went door to door. For the first time, we recently went to King's Island's Spooktacular fall event. It wasn't too over the top IMHO, but I didn't get much out of it. I never did do the haunted house stuff, even as an unsaved teen, though it wasn't out of any moral apprehension then. The older I get the more troubled I am at the preoccupation with death and the occult.
I remember a conversation here on a previous iteration of the forum that involved the subject of a genre of violent film (like the saw series) called "torture porn". It involved, for those who want to go in the way back Nostalgia machine, Patebald (a good guy and former Fundy turned FreeBird) who defended watching that stuff. I thought it was wrong then, and I think it's still wrong now.
There, maybe that'll get this place fired up, lol.