There really shouldn't be a difference. You'll go through the U.S. Consulate for conditional permanent residency based on where you're residing (so probably Guangzhou). There shouldn't be an effect on the I-526 at all. Be careful with the older child: if you file the I-526 after the child turns 21, the child cannot be counted as a derivative beneficiary.
First you need to retain the services of an experienced EB-5 attorney. Second, the EB-5 rules allow any foreign national to file an EB-5 investors petition and the spouse and children can be nationals of different countries.