Have a Story page prepared, called perhaps, AAAA, so that it is always at the top of the index and ask them to enter a name and date on that page if/when they alter something.
If they can't be bothered to assist you there is no real advantage in making them administrators
I believe the last item in the Newsletter tells you who has visited your sight and shows the family name of the altered individuals.
Ted
If you have the Original I would upload it to a NEW FREE SITE, or if you wish to put the site that they are on , back to Original without any of theirupdates, just upload and overwrite it.
Regards
Les