I don't know why age matters. If you're born in the USA you're an American citizen. He says in a video interview about this that he would reject their citizenship and deport them anyway.
Discussion
Well if a jackass isn't dictating the policy.
I would understand if the child br sent with their parents.
I'd give the parents the option of either take the child or put them up for adoption.
The child regardless would be documented as a citizen. So when they hit of age they can immigrant back to the states.
But where's the fun in that.