I have the password for my main e-mail written down in an envelope in a safe which I hope my kids will be able to use to notify everyone on various online forum

I have the password for my main e-mail written down in an envelope in a safe which I hope my kids will be able to use to notify everyone on various online forums of my demise, and one of them to take over my digital assets (over a thousand books in the Kindle store, hundreds of MP3s on Amazon Music).