American son, Chinese husband and my self is Canadian

Cecile, has your husband gotten his green card? If he hasn’t, your son needs to apply for a travel permit. If your husband has gotten his green card and your son was born before he got his green card, he still needs to apply for a travel permit. If your son was born after your husband got his green card, then he needs to apply for a Chinese visa.

I personally suggest you ask from the Chinese consulate or embassy. They can tell what your son needs to apply.