I believe that any base ideas are good. Clearly, you have something in mind already and things you want to explore and integrate into your story, so I'd say you are all set.
I cannot give you advice, I can only tell you what I'd do with such a premise. I'd not try to cram all those elements inside a single short story. I'd take my time and tackle them one by one slowly. I'd probably spend a full chapter setting up the environment and giving a back story to the characters. Who are they, what do they like, why are they doing this job? What do they think about the whole situation? A castle is a very big place and it would take a lots of words to describe it. I wouldn't be able to do it all at once.
Then I'd pick one element that you listed, like a hidden passage. My main character would discover it and while she is looking around or as she is getting in trouble, I'd go back to the past and explain why it was created in the first place and what was going on in there, then I'd come back to my main character to continue the story. This would allow the reader to feel as if it was not just a random trap added there for the only purpose of the story. Perhaps a girl in the past experienced the same predicaments as your character in the present time.
Then I'd go to another element and repeat the same process.
Something like this. Oh, and make sure you enjoy writing it.
