It's hard to answer your question. Safety is TOP Priority over anything, if it is not your top priority DONT OPEN. You can have a couple non costumed staff members be security persons, but you have to remember that anyone can get hurt and you still have to follow local laws. If your city is ok with your haunt talk about how to deal with some of your concerns and ask the local police how they might want you to handle things if you feel this is best for you to keep safe. Your actors NEED to also act as security, they need to be told to "break charictor" if a person going through your haunt gets to scared, for a medical emergency, and if you actor feels unsafe.
I operate a mostly yard display with live actors to just make the heart skip a beat a bit. Nothing to scary and this way I'm in control of how people act or should I say react when you scare them. Things can turn ugly fast when people react to scares the wrong way by your actors getting punched or kicked. It does happen even to the prohaunts!!!!
Most important do your best to be clean and not to graphic and DONT scare the little kids as this could be their first time going through a haunt.
REMEMBER IT"S JUST FOR FUN!!!