Jennifer Garner kept things simple as she celebrated her 46th birthday on Sunday.

"It was a low-key family celebration with kids," a source tells PEOPLE of Garner's Los Angeles bash, which took place two days ahead of her actual birthday on Tuesday.

Elaborating on the party's festivities, which were first reported on by Radar Online, the source adds that "the backyard was decorated with a lot of balloons" and all the "guests had fun making pizza" via a pizza oven Garner rented from Olive Wood Pizza.

Although the party was kid friendly, the source adds that Garner also had a bar with wine and beer.

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Jennifer Garner

However the guest list, which included Molly Sims and her family, was missing one notable face: Garner's ex Ben Affleck.

Although Garner and the 45-year-old actor, who filed for divorce a year ago, remain on friendly terms, the source tells PEOPLE "Ben wasn't there," even though he was in Los Angeles at the time.

"Ben was back in LA this weekend," the insider explains, adding that "the whole family went to church on Sunday before Jen's party."

"Ben is getting his new house ready, but hasn't moved in yet," the insider continues, referring to a $19.2 million home near where Garner lives in Los Angeles that the 45-year-old actor is looking to buy.

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A real estate source tells PEOPLE the house is still in escrow.

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Jennifer Garner and Ben Affleck

Garner and Affleck, who announced their plans to split in 2015 after 10 years of marriage, spent Easter weekend together with their three kids in Hawaii, where Affleck is shooting Triple Frontier.

"Things are pretty good between them right now," an Affleck source previously told PEOPLE. "They are happy to be together" with their kids: daughters Seraphina, 9, Violet, 12, and son Samuel, 6.

"He's found a really good routine," the insider added, describing how the actor flies back "to spend time with the family" whenever his schedule allows it.

This Story Originally Appeared On People