There is a great place in PYM. If you end up in HYA, take a cab to Spanky's Clam Shack (not really a shack) for some great seafood. ACK and MVY also have restaurants on the field as does CQX.
Can't go wrong with BarbyAnns. Try the swordfish tips, and the french onion soup. This is at HYA. If you do go there don't let airport ops park you, you'll end up in an aircraft graveyard, park Air Cape Cod, Much nicer!