We were just at CRT for breakfast on 5/12. Our reservation was 8:00 a.m. When we got to the park there were a few CM's asking if people had breakfast reservations then they directed you where to go. No one asked us for our reservation number but we brought it just in case.
Have a wonderful time. This was our first Disney trip and having breakfast in the castle was amazing. We all thought it was great.
Have a great trip!