Selective Page Content Localization on Front End Only

I’ve been hunting about without success on a method of selective page localization on the front end content only.

MY NEEDS
I only want to have a section of the front end content pages be in two languages.

My example includes a few pages of information on upcoming Day of the Dead activities. I want parallel pages in both English and Spanish.

INITIAL IDEA
Create matching English and Spanish pages with a custom field key of “language” and “en” for English versions. Alternately, use “es” custom field for Spanish versions.

Finally, use some php to create two nav buttons at the top of the page or aside that allow switching between the two languages by accessing the custom field language designations.

Not sure about multipage navigation yet though. Obviously, I want users who prefer Spanish to stay in the Spanish pages. Would be easy, if less elegant, to simply manually drop in next / prev links that go to the next English page from the previous English page (and likewise for Spanish).

NOT HELPFUL
There’s a lot of info about using mo and .po files for localizing plugins and themes. I doubt this is any help to me since this seems to be more about the back end as opposed to parts of content on the front end.

LOOKS PROMISING
I found one article that looks promising but it either doesn’t work or there’s not enough info for me to understand since it failed:
https://www.grobmeier.de/2010/03/12/how-to-localize-wordpress-pages.html