A medieval castle could be defended by surprisingly few people, but not by zero people. And a castle full of people who don't know how to fortify and maintain its defenses eventually becomes someone else's castle.
Aiming for zero required sysadmins in the short term after your own passing, I think the computers you leave behind will run into a similar case of the same general problem in the long term: there's no such thing as an entropy proof system. Castle walls erode and weapons rust if there are no skilled people to maintain them. Computer components slowly break down due to ordinary wear and tear. Software configurations become obsolete and unable to talk with other software, and become less secure as vulnerabilities are discovered over time. If there are no skilled people at all to maintain a familial network-citadel, it will eventually break down and fall into disuse.
Especially with passing, eventually it's like the siege of the Alamo, when the walls do end up breached there's not a soldier there that can do any good.
It's shoestrings anyway and amazing it's working for now :)
It may be highly unlogical, but maybe by shooting for zero it would be possible to bat 1000?
I do everything it takes so that the "extended family" site just works after I leave, as long as the "operator" can keep track of their USB sticks.
Scrap PCs being used as media servers have no internal drive.
Boots to the stick containing the server app.
Accesses media on a second stick containing the files.
Hotplug the media stick to emulate game-cartridge/VCR-cassette convenience.
Upon server failure or massive update, replace that particular stick with a backup or later version, or in the worst case get another scrap PC.
I know, easier said than done :/