Canadian PMs are allowed to acccept gifts from friends and family.
The Aga Khan is indisputably a family friend to the Trudeaus.
Aga Khan is not a lobbyist.
These facts alone are sufficient to dismiss this attempt to create a scandal where none exists.

Must we be so embarressingly provincial in attitude that we are enraged  that the PM is friends with, and an occasional guest, of such a wealthy, generous and respected philanthropist, someone honoured by our own country, as well as being recipients of his generosity eg. The Aga Khan Museum in Toronto?
We knew Justin was the son of Pierre Elliot before Justin became an MP, Liberal Party leader, or the Prime  Minister of Canada. 
We knew Pierre Elliott was no provincial person. He was a world figure who knew and befriended other world figures.
Are we so petty that we begrudge our indefatigable  PM a brief family holiday? That as this columnist insists it should have been a working meeting? (Oddest comment I've heard yet on the matter).