Credit: Michael Tran/FilmMagic

Despite their difficult year, Jennifer Garner has no problem giving her ex-husband props for being a great dad.

For their son’s superhero themed birthday party last weekend, Ben Affleck delighted 4-year-old Samuel by appearing in costume as Batman from his upcoming film, Batman v Superman: Dawn of Justice.

“We all dressed up, I dressed up as a ninja and Ben dressed up as Batman for Sam,” Garner explained while promoting her new film Miracles from Heaven on Extra Friday, adding that it “was the best dad moment in history.”

Asked if her son is excited about his dad playing Batman, Garner gushed, “He kind of is losing it, it’s really sweet.”

The reunion came on the heels of Garner’s bombshell interview with Vanity Fair, in which she spoke candidly about her separation from Affleck, and admitted the actor is the “love of my life.”

After Samuel’s party, Affleck and Garner were spotted taking their children out to dinner at Art’s Table in Santa Monica.

“Jen and Ben seemed fine, you would never think that they are divorcing,” a source at the restaurant told PEOPLE. “They had a fun dinner with their kids and were both laughing a lot.”

Just the next day, the former couple saw each other again at the Oscars. When they initially arrived, the amicable exes were seen standing a few feet away from each other as they chatted with fellow party guests.

Later in the evening, Affleck and Garner shared a friendly hug and a kiss, and at one point Garner held his lapels as she appeared to compliment his look. The two later parted ways, with Garner staying toward the back of the room with close friends Victor Garber and J.J. Abrams.

“They had a nice moment where they caught up and a lot of their friends were there – and they chatted and then they left,” a source tells PEOPLE of the former couple.

Garner’s latest film, Miracles from Heaven, hits theaters March 16.