8 mph cruising speed is painfully slow.
It sounds like it has no changeable gears. This is really impractical, even in flat Florida, unless you are enamored with the singlespeed fad.
A 2 wheeled bike with wire grocery basket panniers would likely have a similar cargo capacity. A two wheeled bike with a trailer would carry more cargo and be more flexible. I wouldn't get a trike unless you have a physical/balance problem which makes it necessary.