It depends on the design of the minivan. The real issue is braking and the transmission -- if you are in the mountains, some minivans will experience warped rotors if you brake for a long time. Some transmissions can't handle long downgrades in low gear.
On flat ground, you would probably be ok, as long as there is a cushion between the weight of the trailer and the towing limit of the minivan. Most people will say "get a big truck," but not everyone can do that.
I towed a trailer about the same size as a Scamp or Casita (but not as aerodynamic) with a Pathfinder (kind of like a beefy minivan). It did ok. My Tacoma does the job better. A big truck would do even better, but I have to use this vehicle as my daily driver, so mileage matters to me.