回复：we would like to return and stay in China, but no idea

If you are Canadian citizen, then you are a foreigner to China. Your Chinese passport was automatically invalid by the time you took oath to become a Canadian citizen, per Chinese law.

As a foreigner, you must have Chinese visa to visit China legitimately. If you plan to stay in China for a long time, you must apply for Chinese PR if you qualify (a lot of restrictions apply). You may also choose to abandon Canadian citizenship and apply for reinstallment of Chinese nationality. None I know has done this so far.