Inside the party, guests were treated to three kinds of specialty drinks, a Bangin' Margarita, Spicy Margarita and Midnight Grove, as well as two food trucks with plenty to eat.
An eyewitness tells ET that Amal showed off her "fun side" at the party and "let loose."
"She was dancing with a cocktail in hand at a private table on the right side of the room," an eyewitness tells ET of the new mom, who sat with Crawford and Gerbe much of the night.
Another fun guest was Jon Hamm, who ET's eyewitness says was "working the room all night!"
"He said hi to several guy friends as he made his way around the main dance floor," the eyewitness shares of the actor, who wasn't seen with a drink. "He didn't appear to be with anyone."