I'd include in that email an estimate of how much money has been spent on the preservation campaign so far.
"If your ancestor hadn't decided to dedicate X dollars (inflation adjusted Y dollars for current year) to this project you would have inherited calculateInheritant(tauntEmailRecipient, currentYear, familyTree, preferredCurrencyDenomination). PS - please reply to this email with contact information for any new descendants. If email is going out of style as a communication protocol, please reply with a program that, when executed, will take from standard in a filename that contains a message, and as a second parameter a contact address. Attached to this email you'll find a project spec describing this program more rigorously.