Furthermore, share the backups and ways to retrieve coins from backups to at least one person who you love and trust the most is key. Accidents (maybe death) can happen to everyone so don't keep all things for yourself alone, then if something bad happens, your coins will be lost forever.
I have a feeling that the chances of the person you "trust' to steal those keys from you are growing proportionally with the value of your coins, and I've heard of enough family dramas to think that there are higher chances for a friend to rob you than for all your house to go up in flames.
Having multiple back-ups is clearly a solution but I wouldn't really deal with riddles when "encrypting" it, one baseball ball in the head and none of your riddles won't make sense anymore.
I don't mention about friends. If I have my wife and my children, I should disclose it to my wife. Even now she does not interests in and have knowledge on bitcoin, I would tell her what to do if I suddenly pass away. My children is too young now so I skip it but if they are older enough to remember what I say, I would say them what to do too.
I agree with you about unnecessary of encryption, that is a way to over complicate everything. Key is enough, just store them secretly and safely.