Another option, of course, is E-Cargo. Or, simply an E-Bike to pull your trailer. Not 100% ideal, but keep it in the back of your mind.
I'd probably try towing the dogs with a regular bike, then if that isn't enough, go for the E-Bike.
Converting from vehicles to bicycles could take some investment. But, consider it this way. No $500 to $1000 a year for insurance, all the gas, car payments, car maintenance, depreciation, etc.