There is an alternative to hiking or biking in order to take in the splendor of Acadia National Park.  One option that you may not have thought of is to take a guided tour of the park.
Operating from mid-May through the end of October, Acadia National Park Tours are fully narrated, three hour  excursions featuring three stops within the park.  Each stop has restrooms.
This is an excellent option if you cannot hike due to health or mobility issues, as the amount of walking needed is very limited.  They can even accommodate walkers and folding wheelchairs.
They describe their tours as:

Our fully narrated bus tour will satisfy even the most info-hungry passenger. Featuring three stops within Acadia National Park, guests will learn about the history of Bar Harbor and Acadia, the geology, the wildlife, and much more, all while taking in in the stunning ocean and mountain views.  Tour stops include the summit of Cadillac Mountain (the highest point on the eastern seaboard), Thunder Hole (an oceanside stop), and either Sieur De Monts Spring (Wild Gardens of Acadia) or the Jordan Pond House.
All tours take place on comfortable buses with an amplified PA system.  The amount of walking is limited and at the passenger’s discretion.  Restrooms are available at our ticket office and each stop within the park.

They open for the season on May 11th and tickets and more information can be found on their website.