updated 07/20/2009 AT 2:00 PM ET
•originally published 07/20/2009 AT 3:00 PM ET
The Gossip Girl star flew 15 high school and college pals from Dallas to New York to celebrate his 24th birthday – which was Saturday – along with his new friends, such as costar Sebastian Stan and actor Toby Hemingway.
“His hometown friends got along great with all his New York city pals,” a source tells PEOPLE.
The whole gang then flew on V1 jets from the city out to Watermill, New York, where they stayed at some private digs for the weekend-long birthday bash. “It was the best birthday Chace ever had because he was amongst his closest friends,” says the source.
The group barbequed, ate, drank and were treated to meals cooked by a private chef, according to the source. They also played games and went swimming. But it wasn’t all chilling on the sand: To raise the excitement level, they chartered a speedboat and went out in kayaks.
And in honor of Crawford’s birthday on Saturday, “They, of course, sang ‘Happy Birthday,’ ” says the source.