It says the adult and child parkhoppers are $172.00 Canadian for a 3 day hopper which comes out to US $138.40 with the current exchange rate. That's a pretty good deal.
4 days are US $147.25 for adults and kids. Thanks for the tip to all our Dis friends to the North!
One thing to keep in mind is that you may be charged a "foreign transaction fee" by your credit card. This fee ranges from 0% (Capitol One, I believe) to 3%. You can take a look at these links for more info, but the bottom line is to call your credit card and ask about the foreign transaction fee.
ETA: I tried to add links to articles from the NY Times Practical Traveler blog and a Wikipedia article, complete with a chart of credit cards & their foreign transaction fees, but I don't have enough posts to add links yet. Sorry!