My 13 year old was also stopped by security and asked a few questions about her identity (birthdate, name, etc.). This made her really flustered and she almost flubbed it. I was there but I felt like it would look fishy if I talked to her at all, so I just let her flounder. It turned out okay (she looks just like her sister and me so I don't think they'd accuse me of smuggling someone else's kid) but I wish I had prepared her for that.
In the future, I would probably remind my kids that the security officers might ask them a few easy questions about themselves just to make sure that all of the information is correct and that they shouldn't worry about that because the questions are easy and all they have to do is to tell the truth.