My Husband and daughter are Saudi Arabian but I am Pakistani. How do visas work for us?

Saudi Arabian passport holders can enjoy free entry to HK and stay there for not more than 30 days, so your husband and daughter don’t need entry permit for HK if they just visit there for less than 30 days.
However, you need to apply for a tourist enter permit for there in advance. You should first prepare the relevant documents containing the filled-out application form, a passport-sized color photo, copy of your passport, the financial support proof, hotel booking record, transportation and accommodation arrangement and your travel plan. After, submit the application to Foreign Affairs & Business Service Office (Chinese Visa Office), CCSC(Chinese Visa Office) or Al sandross international Est. to apply for it, or post your application to HK immigration department to apply. The postal address is as follows:
Receipt and Despatch Sub-unit
HK Immigration Department
2/F, Immigration Tower
7 Gloucester Road
Wan Chai, HK