"They are enjoying their time together," a friend of Affleck tells PEOPLE in this week's issue. "He makes her laugh and she’s a great influence. They safely visit with his family and he works to make sure he is healthy and present for his family. His priority will always be his children and making that work."
Over the Memorial Day weekend, Affleck, 47, and de Armas, 32, spent the night together with his three kids — Violet, 14, Seraphina, 11, and Samuel, 8 — at his home.
A previous source said Affleck is "very serious" about de Armas. "He wants the kids to spend time with her so they can get to know her," the source added.
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The couple first met while making the thriller Deep Water, which wrapped up filming earlier this year. After they finished shooting, the two took a trip to de Armas' native country Cuba.
They then flew to Costa Rica for a romantic vacation where they were seen taking a walk on the beach at sunset and taking pictures, which de Armas later posted on Instagram.
Affleck and de Armas have stuck close since their return to Los Angeles with daily walks around their neighborhood with their dogs.
While the Memorial Day outing marked the first time de Armas was pictured with all of Affleck's kids, a source said the actor "continues to work on co-parenting" with ex Jennifer Garner, whom he split from in 2015 and finalized their divorce in October 2018.
"Ben and Jen work together at that," the source added of the exes who are sharing custody of their children.
Earlier this year, Affleck praised Garner for her parenting, telling PEOPLE in February that he felt "lucky" to have her as the mother of his children.
"When you have children with somebody you're connected to them forever," the actor said. "And I’m very lucky she is the mother of my children."
Affleck added, "I'm very grateful and respectful of her. Our marriage didn’t work, and that’s difficult. Both of us really believe that it’s important for kids to see their parents respect one another and get along, whether they’re together or not."