Just tell them your three year old made a typo when you had him enter his bday info. They should forgive him he's only three. Their kids probably couldn't even type until they were 5 or 6.

Really though I'd probably just go for it. If they happen to look at bday (I ferl they never do) I'd feign horror that I made a ticket typo not passport typo.

But I don't have kids. Maybe too scary for parents.