We camped at Arcadia so I can't help you with room advice. However 2 things I would recommend is whale watching, it takes about 4 hours, and a trip up Cadilac Mountain at sunset. You will really enjoy your stay, Bar Harbor is one of my favorite places I've visited.
Being from the Mid Atlantic we are obviously used to much warmer weather. We were at a sidewalk cafe and it was maybe low 80's with really low humidity, in other words "perfect" for a couple from Maryland. The waiter came out with beads of sweat on his brow and complained about he heat. Across the street was another restaurant with the sign that read "We Have Air Conditioning!". Struck me as weird that a business had to advertise AC, it was like we went back in time to 1962.