Very cool!! I love the idea of adding a QR code for the audio tour. One capability of QR codes is to integrate them with Google Analytics, which would let you track how many people are visiting the park; you could also provide an option to integrate with Facebook/Twitter, and then you could not only get detailed demographic information about visitors but also invite them to collaborate with direct communication. Another idea would be to use them in serialization, where each portion of the park has a unique code, and then using that (anonymized) data, you would be able to track a visitor's path throughout the park, giving you insight into how people are using the park/which aspects are most engaging. There are important privacy/anonymity policies that should be in place, but strengthening the link between offline and online spaces will be an interesting point for a park like this (potential to partner with an AR agency as well).