If your kayaks are short you may be able to use a vertical hitch mount on the rear receiver. If your front axle has enough remaining capacity, you may be able to add a front receiver to carry a scooter or bicycles with warning that sight lines and head lights may be impaired.
I would also be one to suggest a toy trailer for your additional gear. Going with an enclosed model will be heavier than an open frame but will keep all your gear out of the weather and more secure than having everything in plain view. I suggest a model long enough to suspend the kayaks along the wall or from the ceiling. Width should match your camper van - This will allow you to see the trailer in your mirrors and will still be aerodynamic. For the type of items you are bringing, you can stay with a lighter single axle trailer rated at 3500 lbs but opt for axle brakes.