When you enter the world of cryptocurrency, one of your family should know what you're doing. It may be your wife or husband. Someone whom you can trust. You should teach them for them to have knowledge in cryptos. If one day, something bad may happen to you, at least there someone knows your wallet and your investment. The key here is not to be greedy.
I'm a selfish bastard then 
If I'm gone and I wont be able to spend my crypto, nobody will!
But seriously, why would anyone trust their bitcoins to a woman? You know that wife has this legal option to deprive you of your coins right? Of course if she's aware of you having some than why would you make this easier for her...
Leaving coins to kids, now that I would understand. Some cool puzzle in the basement, with clues and tips on how to find the treasure. Something fun and creative for the kid to remember and learn the path of crypto along the way. But simple peace of paper with all the instructions, that actually anyone can read seems like safety protocol breach. I think them coins have the anonymity feature for no reason, it should be used to the max.
Seems like you have trust issues with your wife. Finding treasure is a cool idea. Anyway, we invest in cryptos for our family's future, specifically for our kid's future. Now, if you're gone, and no one knows about your coins, then what will happen to your family? You want to leave your coins to your kids, right? What will happen if they'll find the treasure? Aren't they going to spend it in a useless stuffs? They're still young, and don't really care about the value of money. For me, it is still better to leave your coins to someone who is mature enough.