Nicole Richie and HarlowHarlow Madden's birthday party had a guest list that rivaled some A-list shindigs, and she's only turning 3 years old.

Newlyweds Nicole Richie and Joel Madden threw their daughter a party over the weekend at the Treehouse Social Club to celebrate her upcoming birthday, according to PEOPLE.

"It was a fun, casual party," a source told PEOPLE. "The kids played outside in the Treehouse and enjoyed art and crafts projects inside. All the moms chatted while the dads bonded, and it was a perfect party for both the adults and the kids."

Little brother Sparrow, 16 months, was also at the party to help his big sister celebrate. Guests enjoyed healthy snacks and a special birthday cake, which was presented to Harlow.