One could argue that this is simply an example of bad judgement. However, whether the Aga Khan is a wonderful man or not, and regardless of whether he is a friend of Canada, his foundation lobbies the Canadian government for funds. MR. Trudeau's excuse that this was simply a vacation with an old family friend is shown to be a lie in view of the latest revelation that the President of the Liberal party and another senior liberal MP (together with their spouses) were also on the trip. It seems unlikely that they were both also old family friends of the Aga Khan and the vacation was simply a junket.
It is a clear conflict of interest and all three should resign.