Lauren Bush, the niece of former president George W. Bush, and David Lauren, son of iconic designer Ralph Lauren, celebrated their engagement Saturday in the Hamptons.

Guests included the entire Lauren clan, Paris Hilton’s parents Rick and Kathy Hilton, Lauren Bush’s mother, Sharon Bush, and designers Cynthia Rowley and Douglas Hannant.

Everyone stuck to the all-white dress code at the fete, hosted by Hearst heiress Anne Hearst and her husband, author Jay McInerney, on their sprawling farm in Water Mill, N.Y.

David Lauren’s sister, Dylan Lauren – who recently got married herself – greeted guests at the back door of the house. “I don’t know why I’m standing here,” she joked to PEOPLE. “I feel like I’m the host.”

Out on the back porch, guests sipped cocktails, while inside, they enjoyed dinner served at a single long table and speeches by Sharon Bush and Rick Hilton, who expressed the hope that the young couple’s marriage would be as long and happy has his own, to Kathy.

The wedding will take place at the Lauren ranch in Colorado, and Bush’s grandfather, George H.W. Bush, is expected to attend. The bride plans to wear, naturally, a Ralph Lauren wedding dress.

But one big question remains: whether Lauren will take her husband’s last name, making her Lauren Lauren.

“I think it will be Lauren Bush-Lauren,” the bride-to-be explained in April. “That’s not final, but I think it’s nice to have the same name as your husband. I am sort of old-fashioned in that way.”