My grandparents will travel to Charlevoix QC (see screenshot below) from 3 to 11 Oct 2019. Can they see aurora borealis with the naked eye?
If yes, what are the best places to?
The aurora are centered around the magnetic poles and not the true north pole. Since the magnetic north pole is near Hudson Bay, Canada you are more likely to see aurora at lower latitudes in Canada than in Europe. The U. S. Government publishes a handy three-day aurora forecast map so you will have some idea of the activity closer to the visit. See this link. As with star-gazing the best place to see aurora are far away from city lights as possible on cloudless nights.