Like most we always have discounted coupons etc available before the last week of Halloween. But instead of just raising the price on October 31st, you have your set price the week of Halloween, say in your case $15.00. Then you have an "Early Bird Special" of $12.00 available the first couple of weeks.
The key is that you have the pricing structure located in advance on your web site. Remember you are not RAISING your price on Halloween, but LOWERING your price prior to Halloween!
I have had people at the ticket booth say this ,"Oh you raised the price for Halloween" and I reply "No Sir, this IS the normal price. We lowered it for an Early Bird Special." Then the wife or girl friend tells him "See I TOLD you we should have come eariler!".
Don't forget a VIP line. It's just like printing money.