You speak in contradictions. You say in one sentence "I have been hired to do a halloween magic show...", and then say a short time later "I have not agreed I would do the show yet." So which is it? Have you been hired or not?
Here's my observation, and I'll close with my suggestion, and please don't take any of this as me being harsh, mean, or too critical. I mean to point this out in a very matter of fact way. I'm not trying to cut you down or anything. I really do want to see you be successful in this project. My observation is this: Currently at the time of this response it is October 13th. There is only about two weeks and some change left in this month. If you've been either hired or offered a Halloween themed gig I can only assume it's for a Halloween party of sorts. This also leads me to the conclusion that the party is scheduled to take place sometime within the remaining month. (As not too many Halloween parties take place after October is done.) If you're lucky, you've got at best a little over two weeks to plan for this performance if you accept the gig. At worst, a couple days.
I don't know how you are as a student of magic, but I know for a fact that I have a real hard time trying to learn new material and get it ready for presentation for a show in under two weeks. Maybe if you locked yourself into a room by yourself and did nothing but eat, sleep, and practice sure, but I'm willing to bet you've got school, homework, and other obligations to occupy your time.
I think it's fairly safe to say that going out and buying several new themed effects and trying to build a show around them is not going to happen.
Here's my advice. Theme your current material to have a spooky, but not scary appeal. If it's a party, show up in a costume. (no mask!) Put a Halloween spin on classic effects. Tell the story of the Raven (Edgar Allen Poe) to Linking Rings, Theme your cups and balls to be skeleton head cups (available at Halloween stores) and sponge brains, Do Cookie Cutter from Dan Sperry with an educational message about having parents check their candy after trick or treating, Rice Bowl productions using candy that can be given out, Topsy Turvy Bottles with patter of it being Butter Beer (or Cyder), use your imagination and just have fun with it!
All the best to you! Also, just for your reading enjoyment, I've gone further to outline below my definition of Spooky vs Scary.
Spooky Vs. Scary:
A clown at a theme park that follows you around is spooky.
A clown from the theme park standing in your kitchen at midnight is scary. (I'd actually say terrifying, but then thats just me.)
A guy dressed in all black head to toe is spooky,
A guy dressed in all neon lime green head to toe is scary.
A group of Goth Punks head banging to metal music at the local club is spooky.
A group of bible carrying missionaries from your local evangelical fundamentalist church on your door step at 8 in the morning is scary.
Spooky: Cups and balls using little plastic skeleton head cups (find em at any Halloween store) and sponge brains instead of ball loads.
Scary: Saw from Sean Fields.
You get the picture...