Ben Affleck and Jennifer Garner reunited at Disney World over the weekend with their children, and rather than having fun at the theme park, an eyewitness tells People the estranged couple looked "so tense and uncomfortable."

The source added that Ben and Jen, who announced that they were ending their ten-year marriage in late June, had "no interaction at all" and "when she was around him, you could see the tenseness. Her shoulders would rise up. There was never a point that all of them were really [interacting] together." Yikes! Affleck and Garner spent time individually with Violet, 9, Seraphina, 6, and Samuel, 3, and when they visited Universal Orlando together the previous day (which was Ben's 43rd birthday), another onlooker told the mag, "Neither of them looked too happy."

The Batman star flew to Atlanta, Georgia on Thursday, which is where Garner has been staying with the kids while she films Miracles From Heaven. "As always, it's about the kids and they will always put them first," a source added. "Everyone had fun. They put them first no matter what. All Ben wanted for his birthday was to be with his children."