I am sure American credit card is working there. NO problem at all. They do the automatic current exchange when you shop there with your credit card. Depending on your cc company, you might be charged for a small exchange fee. very small one.
US dollar works there too. It is accepted almost everywhere, at least in Toronto.
Not sure about personal check. Never used that there.
Just bring $100-200 US dollar and credit cards. You should be able to make most of your purchase with your credit card. For some small purchase, use your US dollar. Remember to get multiple pieces of small amount dollar bill instead of 1-2 piece of 100 dollar bill.