Matthew Stackpole has ridden the crest of so many successful Island endeavors for so long, it should be no surprise that on Saturday, July 9, he will receive a coveted Island award. Mr. Stackpole is the recipient of the second Walter Cronkite Award; he will be honored at the 20th annual Seafood Buffet and Auction, a fund-raiser for Sail Martha’s Vineyard at Tisbury Wharf.