I love Trick or Treat!! And DH and I have no problem with older children or teenagers coming to our door and knocking for candy. As long as they are polite, they get a handful of candy bars. We only get a handful of Trick or Treaters because our house is a bit from the road. The most we ever got was about 20++.
We don't have sidewalks here and houses are not super close to each other so many children are driven from house to house. We would drive the kids and walk a bit. Thankfully we live in a nice area and people always gave out good amounts of candy. After just a few streets in our neighborhood, both girls had bags full of candy.
I would be sad to see Trick or Treat done away with. As long as it is done in good fun, I see no harm.