Secret Rooms and Passageways

The kids should have a secret room or passageway from their room that either is just a place to hide out, or also connects to a passageway that takes them to common area, like the library or the music room in the basement.

This could be something like a firemans pole from the top floor to the basement, or a ladder, so they can go up too.  Privacy controls should be in place so that one kid can't sneak into another kids room without their permission.

One of the main floor rooms like the library, should also have a secret room behind a bookshelf or something, that's cozy, and place where someone could go to read a book.