For years I ran 6x12' 2995 # trailer, you just needed to notify your insurance company, but no need to pay additional premium. You have to pay that premium on even a dual axle landscape trailer that doesn't dump. The fact that it serves even more purpose makes it well worth that small additional premium. I will tell you thats a small price to pay, try insuring and registering a 10,000+ dump truck. Just a cost of doing business my friend. Charge a little more to justify a larger expense.
I would recommend having insurance on everything, little trailers and the equipment on it.