Very cool QR related game idea.
You could have the same starting point each week and just by resolving the first URL to a different answer have preset codes located in hidden places so all you needed to do week after week is just change the first clue leading to week 2’s /3’s/4’s follow up series of clues etc.
Should be somewhere central to Manhattan like Grand Central Station etc. and then each week could fan out to different parts of Manhattan/Boroughs
Some smart marketing firm will replicate this here for a big label brand sooner than later.
P.S> Clueless about QR codes? check out my 60 second overview here http://www.Cognation.net/QR