"Anybody - do you have and ideas how to handle stuff like this where one spouse is the computer guru and the other is just a basic user? What happens if the guru bites it? You might have the best backup system on the planet, but if the spouse doesn't know how to locate and use it, they're kind of out of luck."

ABSOLUTELY. Because of what I do for a living I have many many encrypted files and redundant backups which I must assure can be accessed by certain others in case I am incapacitated. I have spread sheet document which I keep up-to-date with full instructions (passwords, accessing backups and other cloud services, and all critical accounts online and on paper). This also includes emergency contacts, doctors, insurance company, etc. with full instructions.
This is in a password encrypted document which is emailed and stored by ME...to my sig. other, and to a practice partner/emergency contact who does NOT reside with me. That file contains everything they need to know and how to access it.... so use top-level encryption and a strong password. It is updated and re-sent every time it changes. I thought about simply giving them access on a cloud-shared folder, but decided to also sent them something they could print as needed.