How are you calculating your towing capacity? Just because your hitch is rated at 5k does mean you can actually tow that much. In any event it sounds like the minivan will push you over at a minimum of 1,000 lbs. That's a LOT on A class C. Calculate the amount you can actually tow and stay within the limit.
Tow capacity is the LESSER of these:
The hitch rating OR GCWR minus the actual weight of your RV loaded for travel (fuel, water, food, people, etc). What's left over is the amount you can safely tow. You'd be surprised how many RV's out there have a 5k hitch but by the time they are loaded for travel have really nothing left for capacity.