Although we love to make the night as creepy as possible for our young visitors, unfamiliar costumes, hands filled with bags and flashlights, and the pushing of many young bodies in too small of a space can create tripping hazards in the dark. Try substituting a Halloween tape of creepy, crawly sounds for the gloomy lighting. Discard anything that you even suspect might have been opened. Fruit and homemade goodies should always be suspect. Unless you are personally acquainted with the giver and can absolutely identify the item as coming from that person when you get home - don't take a chance, discard the item.
Many hospitals offer free x-raying for treats as a community service.
If you are really concerned about tampering, check in your local area to see if this service is available. If you are driving on Halloween - exercise extreme care. The children are excited, many are wearing dark clothing, and most have been known to run into the street without watching for traffic. Don't limit your caution to residential neighborhoods. Busy thoroughfares are just as hazardous.