There are no restrictions or special permits/license required to bring flintlock long-arms (please note that pistols are not permitted) into Canada as Canadian Gun Laws view antique and reproduction flintlock long-arms as reproduction antiques and NOT as firearms. You must declare your flintlock musket or rifle when you enter the country and answer all questions politely and directly. Your purpose on entering the country is to attend the historical reenactment.
Of course, staff at the border crossing at this time are usually summer students and may not be familiarity with the regulations. This why the Chief Provincial Firearms Officers for Quebec will send a notice to Canada Customs regarding this event. We will also provide a welcome letter for your to show at Customs..
You should also register your musket or rifle and have the registration form stamped by U.S Customs before entering Canada. This is a personal property registration and will be checked by US. Customs when you return to the U.S. to insure that you did not purchase the musket or rifle in Canada.
Passports
For U.S. Residents, you may show either a U.S. Passport or Passport Card to travel to Canada.
Other Considerations
Alchohol: Alchohol is limited to 24 cans of beer and 2 bottles of wine per individual. Above that limit may require you to pay duty on the excess.
Firewood: Firewood and raw wood products are not allowed to cross into Canada