Michael,
If you go to
developers.facebook.com/apps, click into your App and then go to the "Advanced' area, there is an Age Restriction setting. By default, it's set to "Anyone (13+)". You can change that to a higher age requirement if you'd like.
We've honestly *never* tested with that setting. Our understanding of how that works, though, is that when set to a specific age, if a user clicks the Login with Facebook button and they are younger, they will get a "Permission Denied" type screen.
I definitely recommend testing with different user profiles when you change that setting to see what it does, but I believe it's what you're looking for.
Hope that helps,
Alex
Content/Age Restriction
