Tons of killer riding up here. Acadia is beautiful and some great restaurants and places to stay. My wife and her girlfriends are headed there tonight as a matter of fact. Carriage trails are more suited for a mtn or cx bike but the roads are a blast.

We ride a lot in the western mountains near Bethel and Sunday River. The "notches", Grafton, Evans, etc. would give you a good challenge (a bit hilly), some spectacular views, and there's usually wildlife (moose and deer) if you're out early. If you're not adverse to moving once or twice while you're up here, I might suggest the Bethel area for a day or 2, then head over to No. Conway NH for a couple. Plenty to do with some great places to stay. The guy that runs the Pearl Izumi outlet in No. Conway is a great resource for that area - he's worth a call.

Give these folks a shout or drop me a note. Happy to help if I can. If you have no time restraints, I would come in September when the traffic backs off and the foliage is spectacular!
http://www.bikemaine.org/