Chinese visa for minor

If your kids are going to China with both parents, then the requirement: a birth certificate that has the names of both parents and authenticated by the government.

If going with only one parent, the following documents:
Birth certificate
The parent who does not go to China, with his/her valid passport, should come to the visa center personally to sign a declaration of consent for the application of Chinese visa and authorization to the other parent to travel with the minor to China.

If going without any parent, the following documents:
Birth certificate
Both parents should come to the visa center personally with their passports to sign a declaration of consent for the application of Chinese visa and authorization to a third person who will be the legal guardian during the stay in China.
If the parents cannot come personally, they need to provide a "Declaration of consent for the application of Chinese visa and authorization to a delegated person to travel with the minor to China", authenticated by the government.