Chances are, it is safe to tell Ian your secrets:
Ian: Mom? Do you know what Gaga is getting you for your birthday?
Me: No, I don't! She didn't tell me!
Ian: Well, I know.
Me: Ian, what is Gaga getting me for my birthday?
Ian: I can't tell you, because then it wouldn't be a surprise. Plus, I forgot. So I will not tell you AND I forgot what it was already.