I can't even begin to say how much of a bad idea this is. If they're going to a field, then that's one thing but these pics tell a much different story.
I did see one Facebook post about this group where they state they had notified neighbours and local police and it was "all ok"! I don't care if they took out an ad in the Globe & Mail, there is absolutely NO guarantee that someone driving through the area won't call them in. The local police are then put in the awkward position of attending anyway. Most police forces are still obligated by policy to attend and confirm there is no valid weapon call.
My mild-mannered alter ego is in the form of a police dispatcher & 911 operator. If this group called this in to give us an FYI, we would be adamantly advising them to not do this! Additionally, most municipalities have bylaws prohibiting the discharge of firearms within city or municipal borders. I'd be interested in knowing if this applies for this area as well?