Storing stuff online with a strong but memorable password makes a fine backup. But, for most people at least those with houses, protected (e.g. firebox) storage in their homes is probably the best primary. (And even if a bunch of stuff were on a USB I'd also have printouts.)
Also the online setup may be confusing to the parents, depending on their experience level. And something may break in the online setup, some update becomes necessary, some library breaks, the server is down etc. etc. Too many things can go wrong. That's fine for a low stakes hobby thing, but not really for the "I became incapacitated" alert system. Having friends check up on you, giving copies of apartment keys to trusted friends and parents, providing some form of access to your bank account to your parents if you trust them, keeping an up to date physical list of banks and other places where you store money and so on is more important.
It's already difficult to keep all this info up to date. Keeping a technical solution maintained is just extra distraction from the main points. The key difficulty is anticipating all the issues that will pop up when you actually die, practical stuff like interactions with banks etc. What will your parents need to know? What untied loose ends do you leave behind? It's uncomfortable to think about these things so most people put it off.
I have my doubts that any human-memorizable password can be strong enough to withstand a concerted offline attack. If what you're encrypting has to stay secret for 10, 20, 30 years (probably not the case for a password database), then it's a complete non-starter.
It's fairly easy to memorize a password with >64 bits of true entropy using techniques like diceware; if you use it regularly and/or have a good memory, 128 bits is completely feasible.
I have memorized a long sentence with randomly chose words out of large pools like geographic names, animal species and names of barely famous people, a random verb etc. Like "Bill Guthridge supplements in Bhadarwa with an Actias Luna" and a bunch of other words. Then translate this to a foreign language. Add more words if you feel more safe. After such random picks, you just get familiar with each actor in the sentence (read wiki pages then delete history) and refresh the whole sentence every 2-4 weeks using a reminder.
