I've never registered to hand out candy, but we're always in heavily traveled trick or treating loops. We ride in the golf cart parade on Halloween evening and throw out TONS of candy. We also leave some big bowels of candy at the front of our site on a table so we don't miss any of the kids while we're taking our kids around.
Trick or treating has only been on Halloween. In past years, when Halloween fell on Sunday or Monday, some had tried to get the campground to allow 2 nights, but they won't even consider it. Halloween activities including trick or treating happen on Halloween.
We budget @ $100 on candy every year and never seem to have enough for the parade. May need to bump that up this year.