Reservations well in advance are necessary for that time slot, but it's worth it. They're also at the Bar Harbor airport. Kayak Rentals and Tours are available on Cottage Street in Bar Harbor. For a half or full day, groups go out and paddle around the shoreline. The Oceanarium is actually three small museums, two in Bar Harbor, and one across the street from Beal's in Southwest Harbor.
Kids love it, and it's a nice diversion on rainy days.
While looking at the maps, you'll notice that there are other towns on the island, specifically along the Western Shore . These are primarily residential, blue-collar areas which don't offer much in the way of tourism. However, you never know when you'll run into that quaint little tag sale. Keep in mind that this is all very subjective. If you're looking to be entertained, or looking for glitz, or seeking a Disneyworld-type vacation, you may be disappointed.