Just this past Monday, August 9th, Canada has implemented a process for fully vaccinated US citizens to enter the country for non-essential travel. In addition to all the basic international travel requirements, their Covid-19 specifics have been released and are posted on AOPA's Canada travel web page here - aopa.org/travel/international-travel/canada
Proof of vaccination for each traveler must be uploaded in their 13-step ArriveCan web portal, available at a link on the above page. To the best of our knowledge, when completing step 3, be sure to select ‘other’ as your airline, then enter ‘general aviation’ in the airline box, then the N-number under the flight number box. This will allow you to proceed to the end.