It's all good flags. lol
I don't know how much money you planned to spend, but I seriously believe your best chances of killing a truely big buck are in Alberta or Sask. Yes, there are big bucks in the mid west, but these 2 Provinces have a greater number of really big bucks. These areas are so remote and unhunted that many of their deer have never even seen a hunter (maybe an occasional farmer), and end up dying of old age. Old age = big racks! Canada is in a class of it's own, and your Dad deserves it!
Guides are many, just do some research. Most importantly, talk to folks who have hunted with a given guide!!!!!!!! Any good guide should be more than happy to supply you with a list of references for you to contact. Good luck.