If you're anywhere near rt 1 and interested in some classic, rustic New England, stop off at Moody's Diner for a meal. Depending on when you arrive, you might consider one of the lakeside cottages they have in their motel ($69 per night for a family of four).
Since you'll be seeing Acadia, you can't easily miss Bar Harbor. We would get breakfast at Jordan's, a little place with terrific Maine blueberry pancakes. Alternately, there's a very good breakfast buffet on the road in to Bar Harbor, it looks distinctively like a large cabin and is well marked. Then grab a picnic with local fudge or a whoopie pie to enjoy for lunch, either in Acadia, or overlooking the harbor in town.
In Acadia, if you have kids, don't miss heading into the welcome/visitor's center and seeing about the junior park ranger or naturalist program at the desk. It's a free service of the National Park Service. There are guided programs throughout the day, coloring and activity sheets, and ultimately the child can earn a patch by doing the educational activities. If you want to splurge a little, there are carriage rides and a little historic house in the park where they'll serve popovers.
What I couldn't find for my life was a good place to stay in Bar Harbor. The Day's Inn or Best Western we spent one night in there was positively disgusting, mildew crawling along the ceiling, damp, and smelly. I get it, it's humid on the island, fair enough, but no hotel has a right to be that nasty. Ask to see the proposed room before money exchanges hands.
Off the dock/off the boat will be even cheaper. Bring your warm clothes! 
Acadia is cold.
