You can apply for a work visa for your wife and son based on your work visa from the China embassy in India with the following documents:
1. Application form which should be filledvappropriately and authentically.
2. Applicant's passport valid for at least six months with at least 2 blank visa pages.
3. One recent passport size photograph.
4. One Passport photocopy.
5. A notice of visa authorization from a duly authorized Chinese organization, namely, Ministries and Commissions of the State Council, the Government of all Provinces, Autonomous Regions, and Municipalities directly under the Central Government, and Foreign Affairs Offices and Bureaus of Economy and Commerce thereunder, and departments and units recognized by the Department of Consular Affairs of the Ministry of Foreign Affairs of the People’s Republic of China.
6. Covering letter from applicant addressed to the visa office.

Photocopies of the following documents are also required:
7. Your marriage certificate and your son's birthcertificate.
8. Physical Examination Record for Foreigner (which can be downloaded from Chinese Embassy website or collected from Visa Office, Chinese Embassy) issued by doctors from an Indian state hospital.

Note: 1.When applying for visa, please also bring the original documents for checking.