Planning on a week on Cape Cod in the Chatham/ Brewster area and 3 days near Falmouth to do Shining Sea Bike Path and Martha's Vineyard. Want to enjoy Martha's Vineyard in a relaxed fashion. Would 1 day be enough? Or 2 day trips? Or would 2 nights on the island be preferable( really expensive)? Would Chatham or Brewster be better for a Cape Cod base?