One more thing you may consider adding is an "app" to help track your children when they head out on Halloween night.
There are several available for all sorts of smart phones. One of them is called Lookout Mobile Security. It helps find your lost phone and back up data. What you could do is download the app (it's free), give your children the smart phone to take with them, and through GPS technology, track their movements from your home computer.
The Los Angeles reviewed that app and several others to help keep an eye on your children for tricks and treats including Google Latitude, Footprints, and Trick or Tracker. The link to the article can be found here.
Have a safe and happy Halloween, make sure the kids get back at a decent hour (or just go with them!) and ration out that candy. I'd hate to see the little ones with a stomach ache.