Katy Perry, Orlando Bloom and Miranda Kerr Celebrate Katy's Birthday

Katy Perry's birthday is truly a magical occasion -- she's not only getting love and attention from her BF, Orlando Bloom ... but also from his ex-wife, and we got it all on video!

Katy, Orlando and his son, Flynn, celebrated her 34th with dinner at Barton G. in WeHo ... and afterward, we captured a pretty awesome moment. After the meal, Orlando and Katy walked Flynn out to his waiting ride home -- Miranda Kerr behind the wheel of a brand new Aston Martin.

Two must-see things in this video: First, the interaction between Katy and Miranda ... they're totally cool with each other, and Miranda even delivered a bday gift. Both Orlando and Katy are super impressed with Miranda's ride.

Second, Katy's skintight pink latex dress! Wow, wow, wow!!! We're guessing 7-year-old Flynn won't be griping about doing anything with stepmom.

It's a really cool modern family moment. Katy even says, "Love you, Flynnie" in front of Miranda.