I live half an hour from BHB, great little airport but gets VERY busy in the warmer months between Cape Air, bizjets, two scenic operations, etc
Cadillac mountain is a must-see. You can see the airport from the summit. Look into reserving a spot to see the sunrise too, it's beyond majestic.
Mainely Meats is a great BBQ joint with killer ribs. They have two locations, both within minutes of BHB, one next to an ice cream shop and the other attached to Atlantic Brewery.
I second the opinion about visiting the Schoodic section of the park as well, much less crowded and you'll pass a great burger joint (The Pickled Wrinkle) as you exit back onto rt 186. There's also a fantastic ice cream stand right next to that.
Fort Knox and Penobscot Narrows Bridge/Observatory are some great sights to explore as well.
If you venture near Ellsworth you can probably get the ubiquitous lobster dinners for significantly cheaper than Bar Harbor. But just a heads up, lots of places are currently closing pretty early, like 8pm. Rather annoying around dinnertime.
For lodging, a fellow pilot buddy of mine runs Emery's Cottages near Bar Harbor. Little hotel-room-sized cottages in a beautiful location right on the beach, and I believe they have kayaks and canoes as well. Not sure what their pricing and availability are, but I can pass you his info if you'd like.