Hi cousins. We've been to Acadia NP a few times, but never rented scooters. In fact, I didn't think they were allowed on the trails, although I could be mistaken.
Even so, the roads are very steep and trecherous in spots. It takes a good four hours or so by car, and given that it's a tender port, time could be at a premium.
The Park is definitely worth a visit, though. Check their Web site, as parts of the trail are currently closed due to damage.