I agree with Nzs. Residence is granted based upon the assessment of your application BEFORE the grant of the visa, and (apart from any Section 49(1) conditions, e.g. about staying in the same job for a certain length of time), there isn't anything hanging over you for AFTERWARDS. Nothing can get a residence visa revoked unless there was any fraud involved in the application, or unless the holder commits a serious crime. And the whole family will get their PR when whoever was the main applicant for residence qualifies, and gets their PR - the secondary applicants don't have any requirements upon them.