Wow, I think you may wear the Smart car out quick and not be happy. A guy down at work bought a Smart Cabriolet. He's 6'4 and 300 pounds and his wife is a good 250 and 5'3. They fit just fine but they are maxing the car out. When he got it, several of us gearheads went over it to look it over. It's really well thought out but it took us 20 minutes to find the engine. (Under the floor in back.)
With the size of the car, why not buy a pickup for a second vehicle and a medium sized enclosed trailer. Haul the Smart in the trailer, use the car as it's meant to be used and you'll even have a roof in case of heavy rain. I've got a 6X12 enclosed and I'll bet that puppy would fit right in there, along with tent gear, and ride just fine.
I tink the Smart is a pretty decent car and might be able to pull a motorcycle trailer. On the other hand, Goldwings are usually used to pull these, or comparable large bikes, and the average Goldwing pulling a trailer has 50-80% larger engine. If you and your sweetheart like the car, tow it.