Reya Benitez listened and laughed. Turning 24 at midnight, she wore a white slip dress designed by Mr. Warren, and bopped in her seat to the beat of Justin Bieber’s “Sorry,” asking the driver to turn the volume up, way up. “It’s my jam,” said Ms. Benitez, the daughter of Jellybean Benitez, a D.J. and music producer.

Sparkling in a see-through gold dress also on loan from Dolce & Gabbana was Gaia Matisse, the great-great-granddaughter of the painter Henri Matisse. “Andrew, do you have any pics?” she asked, turning to Mr. Warren.

“I need to look on my phone,” he said, the soft light of the screen bathing his face.

Las Vegas in the 1950s and ’60s had the Rat Pack. In Los Angeles in the ’80s there was the Brat Pack. Now, New York has become home base to a young, wealthy and itinerant group that one may think of as the Snap Pack. For them, taking photos and videos for Instagram and Snapchat is not a way to memorialize a night out. It’s the night’s main event.

In the S.U.V., the four passed their phones to one another, assessing the goods, texting pictures that they favored.

“Obviously I’m going to put a different filter on it,” said Ms. Matisse, 22 and raised in Paris and New York, as she considered whether to post a picture of herself and her friends.