To be fair, it's probably best to average out over a few years - in the same spot, some years there can be a horde of kids and other years not so many. Weather can make a difference; so too can competing events (like a big school Halloween party) or local customs. But if there are kids around and they generally do want to go trick or treating, whether or not they come to your block is a good test of how walkable your neighborhood is.
As the New York Times noted in an article about some blocks in Cold Spring, N.Y. that traditionally attract hundreds of kids throughout the community:
With new housing sprawling across the Hudson Valley, parents and children want a neighborhood where you can actually walk around, rather than hiking from two-acre lot to two-acre lot. No one can claim McMansion neighborhoods were designed for trick-or-treating. And with safety an issue for parents in a way it was not for their own parents, having one street, section of town, condo project or whatever become Halloween Central has a definite comfort-zone appeal.
Yet another way that McMansion neighborhoods are affecting traditional neighborhoods - now those living in traditional areas have to buy extra candy for the McMansionites. (That's along with suffering the traffic those neighborhoods dump onto our roads because residents of non-walkable neighborhoods have to drive everywhere. And when there's more residential housing going up without nearby commercial services to support it, or any kind of jobs nearby for residents, that means those people are always driving through other communities to get to work, etc.)
If it doesn't feel comfortable trick or treating, it probably doesn't feel comfortable walking anywhere.