Ben Affleck and Jennifer Garner 'Seemed Like Awkward Strangers' Celebrating His Birthday with the Kids: Onlooker

"Neither of them looked too happy," says an onlooker of his 43rd birthday outing

Photo: Getty

Ben Affleck may have rung in his 43rd birthday with ex Jennifer Garner and their kids – but it seems their reunion wasn’t without a little awkwardness, according to one onlooker.

Affleck and Garner took their three kids – Violet, 9, Seraphina, 6, and Samuel, 3 – to the Wizarding World of Harry Potter to celebrate his birthday Saturday at Universal Orlando Studios, where they treated the kids to souvenirs. But “neither of them looked too happy,” an onlooker at one of the shops tells PEOPLE.

“They didn’t even look at each other. They were talking to the kids, but they didn’t talk or even look in each other’s direction,” adds the onlooker. “They seemed like strangers – awkward strangers.”

A source close to the couple tells PEOPLE that they were focused on putting their children first.

“As always, it’s about the kids and they will always put them first,” the source said. “Everyone had fun. They put them first no matter what.

“All Ben wanted for his birthday was to be with his children.”

Another source close to the couple added, “They have had a great weekend and the eyewitness saw them engaging s a family.”

Affleck and Garner, 43, announced their split in June and have been determined to focus on their kids in the wake of the divorce news. In addition to jetting off to the Bahamas for a family trip in June, the pair has spent time together with their children in Atlanta, where Garner is filming her movie Miracles from Heaven.

RELATED VIDEO: Ben Affleck Denies Relationship with His and Jennifer Garner’s Former Nanny

The latest family getaway comes just weeks after news broke of an alleged affair with the couple’s former nanny, Christine Ouzounian, 28. (Affleck sources have repeatedly denied that he and Ouzounian ever had a romantic relationship.)

• Reporting by STEVE HELLING and LIZ MCNEIL