I would suggest you wait until his next college break get a letter from his institution that he is on a short break and will go back after his visit maybe from one of his professors together with his transcript and school ID,make a travel itenerary for a day to day activities and a travel expense bugdet indicate you are his sponsor for his trip and make sure the amount you show won't consume most of your savings as this will be a red flag.. show maybe 1230canadian dollars per week plus airfare to be on the good side plus keep his visit to 2 weeks. I can't guarantee a travel for him but am certain it will work out for him that way