Here's my advice for MDI...my mother lives on the island.
-No, it's not worth it for a paid tour of the park. Drive the Park Loop Road yourself. Then get off the beaten path--walk on a carriage road, take one of the *FREE* ranger programs (pick up a Acadia Weekly magazine at the Ranger station; they list them all by the week.) Take the boat out to Little Cranberry Island and eat at the restaurant there; take the boat back. (Great meal, great setting, great sunset--the boat leaves from Northeat Harbor.)
Gaylyn's, Cafe This Way (esp. for breakfast) and Two Cats are some of our favorites in downtown Bar Harbor.
The Island Explorer bus is FANTASTIC AND FREE and EVERYONE takes it--locals and tourists alike--unless they really love trying to find a place to park in Bar Harbor! It goes everywhere, and is great for doing hikes. (Park one place, hike somewhere, take Island Explorer bus back to you car.)
The operator of the Jordan Pond house--who'd had the concession for over 60 years--was kicked out in an untransparent and frankly questionable process led by NPS nationally (without input from *anyone* local.) In response, many locals are refusing to eat at Jordan Pond house. Who knows what the quality will be?!? Instead, many are choosing to get their popovers at the Common Good Cafe over in Seawall, which is a great community place and the popovers are just as good. Plus, it'll get you over to the other side of MDI, and away from the crowds!
And watch the sunset from the top of Cadillac. You can watch the sunrise, too, but who wants to get up that early?
Feel free to PM me with anything else!