Kourtney Kardashian's ringing in her 39th birthday at a fancy Malibu restaurant, but she coulda gone to Chuck E. Cheese ... because she celebrated with all of her kids.
Kourtney had Mason, Penelope and Reign in tow as she left Taverna Tony Wednesday afternoon. Looks like Kourt and the fam enjoyed cupcakes during lunch, complete with candles ... although far less than 39 of 'em. Penelope got to do the honors.
She also got some bday love from new mom, Khloe ... who posted some fave shots of their sisterly adventures -- with the caption, "I can't imagine life without you!"
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As we reported ... Kourt and the rest of the sisters flew to Cleveland to support Khloe during, and right after, she gave birth to True -- smack in the middle of Tristan Thompson's cheating scandal.
You'd totally understand if she forgot to give Kourt a birthday shout out -- but the sisters got each other's backs.