Password protect page and all its children

Hello,

I’ve searched and found an old plugin but I don’t think it is compatible with the current version of wordpress.

Basically, I’d like to password protect a “members” page and:
1. Not allow users to access any of its children without the password. BUT, they should only have to put in the password once and be able to access the whole tree.

2. Since members is password protected, I don’t want any of its children showing up in the navigation menu bar.

Any help would be great!