after your child get the 旅行证, he/she needs to use his/her US passport to leave US, use the 旅行证 to enter China; then use the US passport and the 旅行证 to leave China and use the US passport to reenter US.
after your child get the 旅行证, he/she needs to use his/her US passport to leave US, use the 旅行证 to enter China; then use the US passport and the 旅行证 to leave China and use the US passport to reenter US.