One mother and her adult son return to their former home base out east after its transformation into a wellness getaway. Gurney's Montauk Resort & Seawater Spa Like most people who’ve experienced the quiet of an off-season Hamptons , I’ve always been awed by the otherworldly autumn-winter light that illuminates East End, Long Island’s green spaces, and the uncrowded soft white-sand shores that are only a few minutes’ drive from any of the area’s towns. These are the places where my son Dante would lie on his then-tiny toddler pot belly, drawing in his notebook or digging in the sand. We’d called Hampton Bays home for over a dozen years, with me commuting daily on the LIRR to work in magazines in Manhattan while his father taught at a school in the area. My son is now 20, tall, and lean, living with his partner three time zones away. I’ve since moved back to New York City , where I grew up (and work on staff for Traveler).…