Securing your private key is quintessence here, but there are some issues pertaining to your private key security what if something happened to you? How can you hand it over if you are already dead, right? These topics are relevant on how to transfer digital assets to your next of kin. I have read about Coinbase having this custodial service, in which they will hold your private keys. If ever something happened to you or in case of any fortuitous event (leads to your death). They will protect your keys until such time your legal heir(s) can provide legal document, e.g. death certificate and/or your will to transfer your digital assets. I think it would not fit to what bitcoin is all about, for it is anonymity currency. Inheritance of digital assets remains a top topic today and securing your private key is the tailback.
Why would I trust Coinbase more than a bank´s safe? What I would do is divide the key in two or three parts and store each on a safe in different banks. For small amounts, just leave it to two people you trust or, for safety, leave copies to four people.