Password protect parent and child pages

Hi all

I am trying a very simple thing (I think):
To password protect a parent page with many child pages with a single password.

I do not want user registration – only to ask for a password.

I need to change the password manually and frequently, so I do not want to have to enter the same password for every individual page.

Ideally, I would enter a password for the parent page, and whenever a user tries to view either the parent page or any of its child pages, he/she should be asked for a password.

Next best would be to mass edit all the pages (parent and child pages) and edit the password for all of these pages at once.

I have searched high and low for a plugin, but only found some that are 6-7 years old. Surely, I am not the only one in the world with such a simple need? ??

Thanks in advance