request for Maine info

Sometime around the end of June I am going to take my 18 year old daughter on a high school graduation trip before she heads off to college. I told her we could fly anywhere in the continental US and stay 3-4 days. She chose Maine. I'm not sure why, but she said she has always been interested in the state and the fact that, unlike SC where she has lived her whole life, they have 'rocky beaches.'
Any suggestions on where we should fly into: Portland or Bangor seem like the most likely spots. I would also like to book a 1/2 day or overnight cruise to see some of the islands and coasts. I'll also be renting a car.
I book my own business and personal trips, but haven't hit anything that has inspired me on the web. I do have the AAA trip book on Maine.
Any suggestions would be appreciated.