As soon as possible! Due to the hamptons being a popular tourist spot during the summer, I would keep an eye out for hotels, air bnbs, etc from the Smithtown/Ronkonkoma area to Brigehampton/Southold area so anything in between but I wouldn't go farther than that unless you are planning a trip to Montauk or something like that.
Tiana Beach Activity Center. 72 Dune Road Hampton Bays, NY
Dress Code: Beach Formal- Light, airy attire is encouraged - Think maxi dresses and linen suits. As our ceremony will be held on the sand, guests are welcome to go barefoot or choose footwear that’s comfortable.