See guidelines here
https://www.canada.ca/en/immigratio...ravel-restrictions-exemptions.html#citizen-pr
Basically need to have proof that they are immediate family members and staying in Canada for min 15 days of which 14 would need to meet the quarantine requirement . Both items may be checked at both checkin in home country and on arrival as would on arrival the quarantine plan.
Personal view would be not a good time to have parents travel unless absolutely necessary given all the restrictions that seem to change day by day but is a personal decision.