So I'm not a meteorologist but an Engineer by trade. A lot of my time is devoted to solving odd problems and in my experience the simplest answer is usually the most likely root cause.
In your case I think the damage was cause by a straight line gust of wind while one side of the tent was open. Three sided structures are against code in a lot of areas because of how prone they are to wind damage. It wouldn't take much for your tent to be picked up by the wind if one side was open and basically turned into a large sail, taking the picnic table with it and causing the destruction you see.
as far as the canoes go I'm not surprised they stayed put. Even though they are light there's nothing there to really generate lift.
Just my two cents.