Choose candy made with Xylitol for Halloween! It is a natural sugar substitute and helps prevent cavities. It will be harder to find than tradtional candy, but is easily found in many chewing gums. This article says to shop online or at a natural foods store.
http://bestdentistnews.com/2011/10/for-this-year’s-halloween-choose-candy-made-with-xylitol/