It is quite a nice area!
I live somewhat close to there but I try to stay away in the summer because it is just too crowded (for me). Fall is an awesome time to visit.
If you are in to hiking you want to check out the Precipice trail. It is pretty rugged with lots of ladders. I wouldn't recommend it to anyone who does not like heights.
Other cool hikes are Beehive, The bubbles and Acadia Mountain.
If you like to bike, you may want to check out the miles of carriage roads where vehicles are off limits. They are a great way to get around the park.
Cadillac Mountain is the tallest mountain on the east coast. There is a road to the top with a great view.
There is also the Park Loop road with many awesome views. Be sure to check out Thunder Hole. It is impressive when the tides are right. Sand Beach is a beautiful place to spend the day but the water is COLD!
As far as off road, there is little in the NP If any?
In Bar Harbor there is the Route 66 Restaurant that I am a fan of.
Enjoy! I hope this helps a bit...