Hi Tran !
A family of four can bring C$36.000 . your wife is Vietnamese , so it is much easier for you . Since getting a PR visa to come to Canada she might ask some banks ( Import - Export bank ; ACB bank ; Sacom bank ) here to transfer some money for her if she can prove that where the money comes from ! .
Moreover, when she is in Canada , each person in her family ( her parents, sisters, brothers )can send her C$ 7.000 per year via a bank , but they need to show their birth certificate to prove that they are sisters or brothers ...
Hanh.