Ahhh, Cape Cod. Used to go there for a week every summer, when my wife's father used to rent a house in North Truro for August, but he stopped doing that about 8-9 years ago, as he's gotten too old (and his 3rd wife died). Anyway, best place for lobster rolls was Clem and Ursie's in P-town, but they closed a few years ago. Used to love just going to the local market, buying a bunch of fresh seafood, cooking it up and eating it on the deck while watching the sunset on the water (we were on the bay side).
Love soft shell crabs, too - always like to get them right at the beginning of the Atlantic season in May at Sophie's in NB (very tasty); see the link. I also enjoy going to Bahr's in Atlantic Highlands at least 2-3 times each summer. Not the most amazing seafood restaurant in the world, but it's a cool place overlooking Sandy Hook, it's usually fresh, and it's a bit of a tradition. Usually get a combo with lobster tail, as I love all seafood.
http://gardenandgun.com/article/here-come-soft-shells