If you're looking for more of an adventure, take the ferry over to Peak's Island to bask in the ocean air before pulling into the charming island town, where you can find a quiet picnic spot, enjoy ice cream from Down Front or a cinnamon bun from Peaks Cafe, and stop by a one-a-kind umbrella cover museum.
There are SO many amazing places to eat in Portland, here are a couple of my favorite lists: https://www.cntraveler.com/gallery/best-restaurants-in-portland-maine https://boston.eater.com/maps/best-restaurants-portland-maine https://www.bostonmagazine.com/restaurants/best-restaurants-portland-maine/