Hi:
Good suggestions so far.
Taking Route 1 is definitively (somewhat) scenic, but it will be a long trip to Acadia that way. Lots of stop and go.
I would recommend going through Augusta or Bangor.
If you take 95 to Augusta you can take Route 3 to Belfast, through Ellsworth, and continue to Acadia. In the alternative you can take 95 right past Augusta on to Bangor, take exit 182A (I395) as you approach Bangor, and go to Exit 5 or 6 off of I395 (I drive it all the time but forget the number) and take the exit (which is Route 1A) through Ellsworth and then on to Acadia from Ellsworth.
On the way to Augusta you can go to Freeport. Very touristy, but LL Bean (in Freeport) really is worth the trip. It is open all day, every day. It never closes. Literally.
If you stop in Augusta be sure to go to Vaughan Woods, also called Hobbit Land. It is a great visit. Easily missed. It is small and tucked away. And, it is free.
Vaughan Woods & Historic Homestead
Belgrade Lakes (about 20 minutes northwest of Augusta), will be busy, but there are great views around the lakes and it is easy to find a tucked away place to relax.
If you drive through Belfast you can walk around the (small) town. It is less touristy and near the water.
Cobbosseecontee Lake (also called Cobbossee Lake) in Manchester (a few minutes from Augusta) can be fun. It will likely be busy, but it is a quick stop and depending upon where you are from you may not think it crowded. You should be able to rent a canoe or kayak or paddle boat. It is fun to look around there and easy to get to.
Morse's is a great place. In the middle of nowhere (not far from Augusta), but well stocked with European (particularly German) food.
Morse's Sauerkraut & European Deli
I normally would recommend Hallowell (a few minutes from Augusta), but there is a lot of construction going on. Hallowell is a small town, kind of like New York/SoHo plopped in the middle of nowhere. It is not to hard to navigate the construction and parking really is not hard to find on side streets if you are ok walking a bit. Good food in Hallowell (which is really just one main street).
Depending upon how much time you have, driving to Lubec from Acadia could be fun. Very rural, but Lubec is the easternmost town in the US. Then you can take the bridge from Lubec over to Campobello Island in New Brunswick (you'll need your passport). Campobello is where Franklin Roosevelt used to vacation. Very scenic.
Hope these are helpful.
Have fun on your trip!