I too vacation in Canada. It's always a pain getting currency exchanged, foreign transaction fees etc. Can you elaborate how you open a Money Market and fund it with USD that gets stored as CAD in cost effective way? Getting currency exchanged is a pain.
I don't do anything very sophisticated. We have a cottage in Canada and have two bank accounts at our local credit union (East Coast Credit Union): a Market Watch account, which pays interest, currently 1%, and a checking account. We deposit checks drawn on our US bank account either in person or by mail. The credit union, and I think many Canadian banks, offers the option of accounts in USD and in CAD, so that you can move money between those accounts easily, and i know Canadians who travel to the US frequently who maintain accounts in both currencies at their bank, and move money from one to another as they need it or to take advantage of a good exchange rate. At our bank the USD account doesn't pay interest, and we opted for both accounts in CAD. Before we opened these accounts, we withdrew money from ATMs with our US ATM cards, and seemed to get a good exchange rate, but paid our US bank's ATM fee. My Chase United miles credit card does not charge foreign transaction fees and seems to get good exchange rates. I read on gocurrycracker.com that these world travelers use a Fidelity ATM card because it refunds ATM fees.
I hope that helps, but others may have cleverer solutions.