I wouldn't get to heavily invested in QR Codes. They are a pain to use for endusers and they don't have a lot of support. In fact, Google has started pulling all their support for QR codes when it comes to the Places in favor of NFC. (http://gizmodo.com/#!5787427/qr-code...-good-riddance).
If your looking for reach your customers via smart phones, may I suggest you provide them with your haunts own custom branded mobile app? You can offer them news, event information, ticketing information, backstories, a photo gallery, youtube videos, coupons, and so much more directly from inside the app. Plus, if it's installed on their phone, you now are able to reach them for year round marketing and advertising. We can create your app and have it on your iPhone / iPod within 24 hours of signup ready for testing. Android and Windows Mobile Apps coming soon! Check it out at http://www.hauntapps.com. Get yours today before your competition does.