Recommendations Kz Sprtsmen Classic 18rbt
It will be very difficult to find a hybrid that will be under 3500 lbs when loaded with propane, batteries, camping gear. There are a few single axle hybrids that might be close to your limit, but check the cargo capacity on them. Some leave very very little weight left to hold essentials. They advertise a low GVWR, BUT ONLY GIVE YOU 250 lbs for your stuff. You'll overload the single axel in no time.
For a minivan I would not recommend a full height trailer. I would look at newer popups (a high wall perhaps), A frames, or trail manors.
The one you've mentioned does leave 800 some odd pounds for cargo so that's better than some of the other small hybrids.
Have you checked the Sienna for any frontal area limits for towing? Some vehicles can handle 3500 pounds when low profile, but once it's a barn door, it's too much to handle.
2015 Coachmen Freedom Express 292BHDS Blue Ox WDH
2015 RAM 1500 4X2 CrewCab, 5'7'' bed, 3.93 gears, 5.7L 8-speed VVT, Payload 1608, Max tow 10,400