It's unclear what the tropical trip is for, but Kourt's daughter, Penelope, just turned 11 a few days ago, and it could also be a babymoon -- however, Travis Barker is missing out, if that's the case ... since Blink-182 is still on tour.
As we reported, Kourtney revealed baby #4 during Blink's L.A. concert last month ... holding up a sign with the happy news -- a nod to the band's "All the Small Things" music video.
The couple later revealed they'd be having a boy during their gender reveal ... shooting blue streamers into the sky after a drumroll by TB himself.
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BTW, Kourtney also showed off her bump week, looking as fantastic as ever -- so, expect to see more of her as she awaits her next bundle of joy.