The app we're building wants to notify all of its users that there is new information available.
Basically, the users follow hints to find a certain place on a map to win a prize. For a couple of weeks there will be new hints available at specific times, 3 times a day.
We're now looking into using App-to-user requests but the requests stick around, unlike a message in there news feed, so it might look spammy. It also doesn't get the message across directly but just shows "App has a new request for you".
What is the best way to let all of the users know that the new hint is available? We don't want to force them to like our Page. We don't want to e-mail them either.