We have a great system which we started in our village about 10 years ago. It is made public who is willing to have trick or treaters call.A list is collated, (usually in the pub).This started when a friend organised a halloween party for the village children and some of the parents volunteered to dress up and take groups of children round to an agreed list of houses. A great time was had by all, the houses visited had all been decorated and many of the adults waiting for the trick or treaters dressed up too.
Everyone enjoyed it so much that this is now a tradition and the list of people willing to have their doors knocked on has grown.Our children are now much older and don't have a halloween party anymore - but many still go round in their groups because they now escort the young children round "the route".We are very lucky in that we have well behaved, polite young people who don't knock on doors where they are not expected. Many of the old people in the village join in and enjoy being visited by this lovely, lively bunch who always have time to chat, say thank you and wouldn't dream of upsetting anyone.I'm proud of them.
Can't see this working in most places though!