All hail the King! Tyga's son King Cairo celebrated his 3rd birthday with celebrity pals, on Friday. Kanye West brought daughter Nori and Kourtney brought her trio - Mason, Penelope and even baby Reign, to Racer's Edge indoor go-kart warehouse in Burbank.

The car theme was carried through to the fire truck inflatable slide outside in the parking lot, where even Chris Brown took a turn plunging down the steep slope ... with a drink in hand! Later, the singer tooled around on a bike while smoking a cigarette (how appropriate for a kids' party!), while daughter Royalty played with her friends.

Proud papa Tyga brought in loads of presents for his son, while girlfriend Kylie enjoyed some snacks from a food truck. The youngest Jenner and Kourtney were the only members of the Kardashian clan to make an appearance, as the rest of the family is holding vigil as Lamar Odom fights for his life in a Las Vegas hospital.

If this is what a three-year-old gets for his birthday, imagine what these kids will be doing for their sweet 16!