Kim K & Kanye West Roll Up in Lambos with Kids, Party w/ Brad Pitt

Kanye West and Kim Kardashian are keeping things balanced in their lives -- hanging with their kids for lunch Sunday, but then partying with Brad Pitt later.

Kimye and half their brood -- North and Saint -- hit up the fancy joint Crustacean Beverly Hills ... rolling up in style with not 1, not 2 but THREE black matte Lamborghinis. The couple actually owns 5 of the whips in total. Check out the vid ... when the late lunch ended, the kiddos jumped into their own Lambo.

After mama buckled 'em up ... Kim and Kanye jumped into the lead Lambo and drove off. They headed to a fancy crib in the Hollywood Hills where they rubbed elbows with Andrew Garfield and, of course, Brad.

It's unclear what the occasion was that brought them all together, but it was just the latest celebration for Kim, who's been partying like a rock star almost nonstop since Thursday's 35th birthday bash for Khloe.