First the plaintive request: if your kids are trick-or-treating, please consider taking them to the houses immediately around you in addition to wherever else they're going. I know sometimes they're going with someone in a different neighborhood or a different part of the neighborhood or whatever, and that's fine. It's just that there are so few holidays that explicitly involve the neighbors that I hate to see one fade out of use as such.
Okay, the grinching: people. With a small handful of exceptions, your child is almost certainly able-bodied enough to trick-or-treat without a car. If you are driving to get to a neighborhood that's better set up for trick-or-treating than your own, please park the car at a park or on the street somewhere or in some other nearby parking area and walk from house to house. This sounds really basic, but I have seen parents driving from driveway to driveway, picking their kids up after each house and driving them to the next house a few yards down the road. This is not okay. You are sending the kids off after lots and lots of sugar--you want them to wear themselves out. And really, if you save a little time and get to more houses this way, where's the benefit? Why get to more houses when you're doing a perfunctory job of the whole thing?
Also, if it is not icy and slippery out, go to every house with its front porch lights on! Don't skip one just because it has a lot of stairs! No, I'm not just saying that because my house has a lot of stairs. I'm saying that because, "Eh, I don't feel like climbing all those stairs," is for people who have an actual physical disability, not for sturdy, healthy children.
I am also a person who firmly believes in taking turns opening presents at Christmas. Even the smallest kids can learn about taking turns--albeit with judicious allocation of turns if you have a large crowd--and if the point was having stuff, you could just go buy yourself a bunch of stuff you like and leave your friends and relations out of it. (If your friends and relations are horrible, odious people, I actually recommend this course of action. But if not, spending the time is its own gift.) If trick-or-treating was only about candy, you could go buy a couple bags of your family's favorite kinds of candy and call it good and not have a couple of Mounds bars hanging around the house until after Thanksgiving, when someone who likes coconut finally comes over for a visit. It's not only about candy. It's the whole experience of going house to house in the dark, scuffing your shoes in the dry leaves or slurping through the wet leaves or trying not to fall in the ice and snow; it's the year that you were finally old enough to have your own way about not wearing your parka and you found out what your mom was on about all those years; it's the way your legs get really tired and you decide that maybe filling the whole entire pumpkin is not completely necessary. It's finding out that someone accidentally left their porch light on but isn't actually home, and you have to trudge back down the walk with no candy. That's how it goes; that's part of the thing. It's about knowing which of your neighbors is the really awesome guy who gives out full-size candy bars and which of your neighbors gives out raisins. If you teach your kids that Halloween is about more, they won't notice all the ways in which it--like the rest of life--can be about better instead. And that's a hell of a thing for them to have to unlearn in their adult lives when you can just do real trick-or-treating with them now.