Instead of "Doctors who kill", be really scary to your customers , be "The 13 year old boy who is nuts enough to have a haunted house in his yard!"
The main reason I say this is because as a 13 yr. old you will never be very convincing that you are any kind of a threatening persona /doctor.
Of course at your age if you are too good at acting like a life threatening 13 yr. old they might lock you up!
"Sorry for making you have to wait, I know the sign said we would be open at 7pm but then I decided to kill my parents early since they were giving me so much crap about my haunting here, but it's OK, now I can Really go whole-hog and you will see how scary this can get!"
Read my last post under the heading of haunt actors and see what I do here as far as acting and storytelling goes.
I do have quite a many advantages over you but experience doing this kind of thing is probably the biggest one, and a word of advice/warning, you will never be able to put a scare into everyone only major politicians and well known terrorists and media commentators can usually do that.
Good Luck, have fun!