Hi, and good luck with this! Evernote is ideal for you both; it's stable and mature (like us, lol) and is built around notes, rather than links between notes, which is the fashion right now. I just returned to Evernote after about 8 years, and all my notes were still there, safe. I did return to a lot of bugs, and a lot of controversy, but these are all about the new features / features taken away, which won't affect you. I'm still seeing loads of bugs, but they are all in the "home" and really not that important.
Notebooks and tags are easier to explain in evernote than in some other apps, because in evernote you can't keeping nesting notebooks - which are really folders - forever. In evernote you can put a note in a notebook - with other similar notes - and you can put that notebook in a stack - with other similar notebooks - and that's it. It's like this:
I have a certificate I want to keep, so I put it in my old wooden box - that's the notebook. I find some more certificates, so I put them in the old wooden box too. I've got some bank statements, I don't want them with the certificates, so I put them in my blue biscuit tin (this is a second notebook).
I know I've got more certificates and bank statements to file away later, so I put my old wooden box and the biscuit tin in the dresser - which is a stack. This keeps them apart from my recipes and my books and my music, which will go in other notebooks and then into other stacks.
Notebooks and stacks are like "places"; everyone has to be somewhere, but we can only be in one place at a time! Tags are different, they are much more powerful, because a note can be "in" multiple tags. This will make finding what you want a lot easier. This can be a little harder to get to grips with, but there are some tag masters here in the forums who will help. I would suggest you start by putting things into "place" - notebooks and stacks, and when you have your evernote "house" set up, start playing with tags and searches to pull up the stuff you need.
Good luck!