how can get visa from embassy?

Martha, you need to get one entry permit for Hong Kong and another one for mainland China. That is, you need to submit two applications to the consular office for both you and your son.

To apply for HK entry permit, the following documents are needed: passport, passport copy, application form, recent photo, financial standing proof, inbound and onward tickets, travel itinerary, and hotel reservations.

To apply for mainland entry permit, submit the following documents: passport, passport copy, application form, recent photo, round-trip tickets and hotel reservations.

Note that the two application forms mentioned above are different.