The Scavenger hunt is a nice idea for marketing and for the community, but could you just make the content automatically available to all players once the codes have been found? Once found, all the codes become public, and the majority of players who use the codes are just going to copypaste the codes from the forum thread. So for most players the hunt will not be a hunt, but just some copypasting. Making such an activity necessary just gates content behind unnecessary busywork. Besides most players will probably not even see the Scavenger hunt info and will thus miss out on the extra content.
