Thank you very much! And

Your reply is very helpful. We are exactly in the same status as you were before.

I think the what the local police department asked my in-laws to apply right before the before baby leaves for US is the 离境证, but at that time the 旅行证 is already expired, will this going to be a problem? Since the 临时户口 is valid as long as the 旅行证 is valid.

If you don't mind, could you please tell me if your son stayed in China longer than the time allowed in his 旅行证 without have the 旅行证 extended?

Thank you again, good night!