The visa officer has to be satisfied that the sponsor and applicant will not be going on welfare when they get to Canada. So in cases where the sponsor is not working, it is a good idea to include a plan in the application showing how you will be living and supporting yourselves once you get your PR.
This plan can include details of where you will be living in Canada, where you hope to find a job, where your wife hopes to find a job or if she plans to go back to school or stay at home taking care of the child, what money you will be living on until you get a job, and so on. Then include proof of whatever you can. So including things like the following will help: an affidavit from your father saying that he has some land in Pakistan and will be selling it to give you money to live on; an affidavit from your wife's mother stating that you can all live with her when you first arrive; proof of any job searches or offers you have received; proof of any savings you have; etc. These things can also be used to show that your wife plans to move back to Canada once you get your PR. Other proof could be things like enrolling your child in school, daycare, activities, etc., in Canada, or searches about such things.