Its so easy, before you die or when you know that you have health issues or your life is being threatened, then simply make a note that your family can only open when you're gone. That note should contain not just the keys/passwords but also on how they are able to get the funds.
The point is, though, that not all of us will have that "advance warning" of when we are going to die. Some die suddenly without warning in the prime of their lives and seemingly in perfect health. So there is no guarantee that any of us are going to wake up tomorrow. You cannot wait until you are on your deathbed to make preparations.
Trusting your wife is the worst possible thing you can do. No one should be so stupid to do that.
I won't ever grant anyone access to my coins, not even partly. When I'm no longer part of this world, my coins will be 'burned' for ever. I don't do it because I want to gift other fellow Bitcoiners extra value now there are less coins in circulation, but it's a principle thing. I'm not being selfish. Why is it selfish to just have your coins go down with you? I'm in no way obliged to help anyone who didn't do shit to deserve even one single satoshi of mine.
Who's there to help you? Family members are mostly just as much of a snake ready to bite when you're not looking. No thanks.
As we each have our own reality, I feel very sorry that you are in this position. I know that for many people, this IS reality. I am so very thankful that I have a wife that I can trust with 100% certainty. We live our lives (not without disagreements) in a full partnership as to our financial circumstances. She is not at all into crypto and knows very little about it or even how much I have - which isn't much... but she knows that I have it and she knows how to get it if something happens to me. As it becomes more and more mainstream, I am sure she will learn more about it as well.
But she at least knows that it is there and knows how to get to it. I suppose because I do not have millions (or even thousands) of dollars in it - I have no concerns that she will 'steal' anything from me. But I consider it to be her money just as much as it is mine. I just have the current 'control' over it. I would be upset if she wiped it out clean without consulting with me first - but I also know that she wouldn't do that.
I guess some might consider me naive (or "stupid" as the above quote states), but it is a wonderful thing when you can truly trust your spouse and know that you are absolutely in this life together!