You are not a Kennedy. Your chances of getting asked to the family’s up-island compound are, frankly, slim. So what? You can still live like American royalty at the nearby Beach Plum Inn. Its 11 rooms and cottages are flush with shabby-chic furnishings and Egyptian cotton linens. Its BYOB restaurant is lauded for upscale surf and turf. And the view of the surrounding gardens and Menemsha Harbor is, in a word, unrivaled.