That is nice that you are interested in learning about and preserving your family history! I know some people who came to the US as Displaced Persons after WW II and that experience was not pleasant. Some will not speak about that while others talk about it. So perhaps you should not be so direct with your father,perhaps you should begin with some general discussion about his life as a child. Maybe he will open up a bit more.
To continue do you know the city/town/village of origin? If not then perhaps the place to begin is with Canada Immigration records. Below is a Canada web page just for that purpose, which will give you some info on how to proceed. http://www.genealogy.gc.ca/10/1008_e.html