EXCLUSIVE: Inside Ryan Lochte's 33rd Birthday: PDA With Fiancee Kayla Rae Reid and an Amazing $100 Bill Cake!

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Ryan Lochte celebrated his 33rd birthday in style.

The Olympian had a night out with fiancee Kayla Rae Reid and about a dozen close friends on Wednesday in Los Angeles. ET has exclusively learned that the group started their night out with a dinner at BOA Steakhouse, noshing on Brussels sprouts, mashed potatoes, steak and tuna tartare while sipping on cocktails.

But it's his cake from Reid that stole the show.

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"His friends brought him balloons and an array of presents, and his fiancee brought him a customized cake in the format of a $100 bill with his face engraved in the middle," an eyewitness tells ET. "It was presented at the end of their meal with sparklers. His friends sang 'Happy Birthday' so loudly to the point that other restaurant-goers chimed in too."

And the party wasn't done yet. Two hours later, the new dad and his pals left dinner and the celebration continued at Warwick LA, co-owned by JT Torregiani and Sylvain Bitton.

"He was presented with another birthday cake and was so pleasantly surprised," the eyewitness shares. "Ryan and Kayla shared a kiss. They never left each other's side."

Lochte left the venue with Reid hand in hand. "They were smiling from ear to ear as he carried out his happy birthday balloons that he was given," the eyewitness says. "They were holding hands as they walked to the car."

Not surprisingly, Lochte's newborn son, Caiden, was apparently on the swimmer's mind during his night out. Another eyewitness overheard Lochte talking about how much pride he takes in being a dad, and was telling his friends that he calls his son a future Olympian.

"It was a special affair celebrating his family, his birthday and the birth of their child," a source tells ET. "He couldn't be in a better place."

Reid gave birth to baby Caiden in June, and since then, the couple has proudly shared adorable pictures of their first child. Lochte's actual birthday was on Aug. 3, and Reid Instagrammed a picture of their low-key family outing for the occasion.

"Last night ❤️Happy Birthday @ryanlochte #loveyou #teamlochte #family," she captioned a pic of Lochte feeding Caiden a bottle at a restaurant.

Earlier this month, Lochte also Instagrammed a milestone moment with Caiden.

"This is something I will always remember for the rest of my life," he wrote next to a snap of himself holding Caiden by a pool ahead of the U.S. Open in New York. "My son watching his dad swim for the very first time."

PICS: Ryan Lochte and Fiancee Kayla Rae Reid Share First Adorable Pics of Son Caiden Zane: 'I'm in Awe Every Day'

Clearly, Lochte is in a more positive place after his Rio Olympics scandal. In June, he opened up to ESPN The Magazine about suicidal thoughts he had following the headline-making incident and his subsequent 10-month suspension.

"I was about to hang up my entire life," he said.

Watch below:

-- Reporting by Brendon Geoffrion and Marisa Fassino