I'm glad that you pointed that out about not being able to alter history once it's on a blockchain. If you read Homo Deus and agree with its conclusions about AIs, this is even more encouraging, because my guess is that an AI would trust things on a blockchain more than on a stand-alone Website.
And that's a really interesting tidbit about your great-grandfather. That's a story that maybe you should document :-).
RE: Summer Vacations