This is the "official" Find A Grave Fan Page
on Facebook. It is managed by Find A Grave and they seldom post anything.
There are no official Find A Grave "groups" on Facebook. They are all unofficial, started and run by fans (or not fans).
To find out who the admin(s) of a "group" are, click on the Members link at the top of the page. On the page that comes up, click on the drop-down arrow next to All Members and select Admins. Do you know those people?