Acadia is gorgeous. My wife and I had a blast there last year. We did the typical hiking, camping and beach thing. We also went rappelling and really enjoyed it. I hope that you have better luck finding decent food in bar harbor than we did. We ate out twice and both meals were awful. I remember one of the places, The Mad Hatter's. Avoid it. Horrible food and worse service. Can not remember the other place.
Portland is a different story. There is an abundance of great seafood places. However, you need to make it a priority to visit Duck Fat.
http://www.urbanspoon.com/m/r/259/1412737
Great place for lunch or a casual dinner. Bistro/cafe style restaurant. Really neat atmosphere. Sandwiches and paninis are unique and tasty. I had the spicy italian panini and loved it. They have the best fries (frites) that you will ever eat. Save room for dessert too. Beignets were incredible and the "Original Milkshake" was one of the best things I have ever had.