Transit without Visa for 2 Years Old

Hello,

This website has been very helpful in stressful times! My wife and I are traveling to Taipei next week. Our plans have changed and we're now bringing our 2yrs. old son with us, and we realize we won't have enough time to apply for his China Visa.

We're wondering if the following is acceptable, given both my wife and I have a valid China Visa's.

A: Canada to Taipei
B: Taipei to Shanghai
C: Shanghai to Canada (under 144 hours)

Do I need to bring my son's birth certificate? Or does the general requirement of travel docs and international passport will be fine? Otherwise, it may be better for us to change all our return flights.

Thank you in advance!