Since I am not too familar with Canandian operators I can't give any names, but I can give you a few suggestions. First of all what do you plan to do with rating? If your getting it just to get it, a 172 is a good choice. If you want to use it professionally, I would suggest you talk with several different operators and get their feed back. And by that I also mean charter (bush) operators. I would go with one who would also employ you after the rating.
In preperation, I suggest that you study the book by Jack Frye. It is one of the best books about how to fly floats.
And enjoy the rating, it is fun. And remember, there are float pilots who have gone swimming and those who are going to.
Richard