The bulk of Acadia National Park is on Mount Desert Island (MDI). There are two ways to get there, by ferry out of Winter Harbor or driving (which takes about 35-45 minutes). I’m not an expert on this area but it’s worth a visit. Bar Harbor is the area where you will find lots of shopping and dining. There is a nightlife (by Maine standards). There is a self guided walking tour you can take through the town called Museum in the Streets, and I recommend it. It will take you along the Shore Path to see some of the original homes in the area. On one of the stops, during low tide, you can actually walk across to a little island that is otherwise inaccessible. Just be sure to get back before the tide comes in!
There is an airport in Bar Harbor and they offer both bi-plane and glider rides. I know people who have done both and they say it is an awesome experience. Most of the whale watching and Puffin trips leave out of Bar Harbor. Most of the time you will need reservations but be sure to ask about their cancellation policies.
Also in MDI, there are quaint towns like Southwest Harbor and Northeast Harbor. I don’t know much about them but they do have shopping, pretty views, etc.
The most impressive thing to do is visit Acadia National Park and go through the Park Loop road. You can drive or bike it. Within the park, there is a network of Carriage Roads that are not accessible to cars…only foot traffic, horse drawn carriage and bicycle. Very pretty and built by the Rockefellers, fascinating story. There is lots of hiking. Jordan Pond is a great place to eat, famous for their popovers. Echo Lake is a nice place to take a swim. If you don’t want to drive through the park, there is a free shuttle that will take you through. If these things interest you, you should calendar some time to spend there in Acadia.
Between Ellsworth and Gouldsboro, you will see a turn off for Tunk Lake. There is an area out there, west of US1 called Schoodic Mountain and Schoodic Beach. This is a great place to hike. You can google for more specifics. Back in this area, you will also run across a path called the Sunrise Trail that goes from Brewer nearly all the way to Canada. Not accessible to cars, people use this path for four wheelers, snowmobiles and bikes.https://sunrisetrail.org
In Hancock, there is a great restaurant (fine dining) called the Crocker House. I absolutely love this place.