Make sure that you alert your credit card company that you will be traveling, with approximate dates and locations before you leave the US. We use our credit card rather than a debit card due to the reduced liability if there is a problem. VISA has been terrific in those situations.
We frequently travel internationally, and a passport or enhanced driver's license (probably not available in CA?) is usually required to exchange money, and certainly to cross the border.
We have a business that gets many Canadian visitors. We allow customers to use CDN money and exchange it at the official rate. We give change in either USD or CDN (if it is available). We will often give US coins back in change at par. We get nice comments about that service. Some businesses near the border may also provide that service for you.
Know the exchange rates (and fees) to see what works best for you. If you are staying in a CG or RV Park near the border, other campers may have money to exchange as they leave the country?
Have fun.