Google has an Inactive Account Manager: https://support.google.com/accounts/answer/3036546?hl=en

Inactive Account Manager is a way for users to share parts of their account data or notify someone if they’ve been inactive for a certain period of time. To set up Inactive Account Manager, go to www.google.com/settings/account/inactive and click Setup.

I've done this so my family can access my Google account. I also intend to write a letter to my wife with my password manager password, which holds the keys to the kingdom.

I have been thinking of setting up a Secret Sharing model (http://en.wikipedia.org/wiki/Key_distribution) and giving parts of my key info to each of my 5 children.

This exact thing is why I keep a physically printed master list of passwords in a safe location, accessible (if not convenient) to my heirs.