Riding a Tandem Bike

While on Mackinac Island, MI, where no motor vehicles are allowed, we rented bikes for a couple hours. I took our younger son on a seat on my back wheel. My husband rode a tandem bike with our six-year-old son behind him. Thing is, on the tandem bike, the adult seat in the front did not have adult pedals or spacing. My husband's legs were moving like he was doing the doggy-paddle the entire time. Also, our six-year-old didn't mind all the hard work. He told his dad that he could relax, because he (our son) had things covered equally. Dad would pedal going up the hills, while he would pedal going down.