As a NH native, summer RV Resident of Wells, Maine, and a lifetime camper, I concur with what others have said about splitting up your time.
I'd like to suggest you consider spending 4 to 5 days in Wells, Maine. There's a great RV CG with harbor views. Family owned, friendly, with nice sized lots. SeaVu, Route,1, Wells ... I camped there for 10 years with my Jayco popups, before buying a park model home at their other rv park, Seavu South.
Wells has great beaches, seafood restaurants, shopping, etc. It's an easy 30 minute drive to charming, historic Portsmiuth, NH, York, and Kemnebunkport, Maine. Portland is also an easy 30 minute drive. There are great amusement/water parks in Portsmouth, York and Saco.
Then, from Wells, take an easy 4 hour drive to Acadia and Bar Harbor, stopping after 2 hours to stretch and enjoy the beauty of Camden Harbor, perhaps a short drive to the top of Mt Beattie.
Enjoy 5 days at Acadia, seeing all that others have recommended, and then take the time to drive to the White Mountains of NH. Drive up Route 16 to the Conway region, do Storyland, Santas Village, then back down 16, across the Kancamaugus Highway, walk to Sabbaday Falls, see Rocky Falls, travel up route 3 and see the Basin, Glen Ellis Falls, Franconia and Crawford Notches ...
Have a wonderful time, wherever you go and whatever you do!!