My family always liked to rent the four-person "buggy" or "Surrey" bike, because if one person doesn't feel like peddling, it's no big deal, (so long as there's at least one person on each side, (3) to even out the peddling) .I do understand there might be more complications to your condition and it's not always so simple as "peddling with one leg" and I don't know whether or not you're capable/inclined to peddling at all. I believe they also have electric buggy rentals, and others with motors. They may have golf carts, too. I'm sure if you call one of the bike-rentals they can help you or recommend something, and if they don't have it they might point you to the place that does - people there have always been really helpful in my experience.
They do have tandem bikes and I think there's even a 4 person 'buggy' at the bike rental place. They looked like each person would only use one foot to pedal with so that might suit your particular needs.
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