You must realize that nothing is risk free in our life. You got to make the decision based on your family, savings, and long-term plan.
You have a CS bachelor degree already? If so, do you have to make money to support your family now, or when? Do you (or your family) plan to go back to China?
If you are the only bread-maker in your family (assume you have 1 or 2 kids) and your family would like to stay in Canada, it is probably more practical for you to go taking the volunteer job and perform well to land a potential full-time job in the company later on - This is the process that lots of Canadian companies take to hire employees (Starting from volunteer, term, or contractor position; transfer to permanent position based on performance).
If what you are coming here for is to get a Canadian passport after a few years of stay here; and you (your family) eventually want to go back to China. Stay here in Ottawa, take more special student courses, get your Master and even PhD. With that PhD, you go back to China.