Don't worry, if they DO release smallpox, your kids are as dead as everyone else's, whether they go trick-or-treating or not.
That is exactly what I've been thinking as I read these posts. Smallpox is so very contagious that we can't really do anything about it, can we? If Smallpox is the next bioweapon, then we had better get the cemeteries ready. Remember, smallpox is a virus. There are no antibiotics (which work against bacteria) which will work on viruses. Go see your local priest, rabbi or minister and be prepared.