Get some Canadian cash before you cross the border. Either an American Express office or your local bank, though that might take a day or two. Once you're 20 or thirty miles from the border, businesses won't know the exchange rate, any more than you do on this side of the border.
Check the US and CN customs sites for current info on what you can take and what you can't. DON'T lie to the customs inspector. If they ask you a question, they already know the answer. On my way north, I crossed at Sweetgrass, MT. and the customs inspector asked if I'd ever been fingerprinted. I told him maybe when I joined the Navy, but I couldn't remember. DUH, my fingerprint was on my passport that he had in his hand.
Since my RV already had miles and kilometers on the speedometer, I wasn't too concerned. Until I stopped at a deli and everything was sold by the gram. So I ordered 8 slices. And I still don't know the conversions. Or the yards/meters conversion. Going thru Calgary, I came to a bridge with a vertical clearance posted. So I pulled over and did the math. I was OK. BTW, crossing into and out of Alaska and back into the US at Sweetgrass, I barely had to slow down before being waved on thru.
Gasoline in Canada is sold by the Liter in Canadian Dollars , so unless you know those conversions, just ask them to fill it up. Attendants pump the gas up there anyway. No choice. Your credit card company will do the converting. And finally, Tim Horton's is the Canadian Starbucks, and they're everywhere.
One other thing. My RV is 30 AMP, but some CGs in Canada had only 20 and 50 Amp outlets. Glad I had pigtails with me.
Retired and visiting as much of this beautiful country as I can.