Halle Berry and Olivier Martinez continue to keep their split amicable, as they stepped out together to take the Oscar winner's daughter Nahla to a birthday party on Saturday.<br />The actress and Martinez, who filed for divorce in October, were photographed driving together on Saturday.<br />A source tells PEOPLE they took Nahla to a party in California's Woodland Hills.<br />Martinez, who was still wearing his wedding ring, is "very happy that he and Halle are able to keep a good relationship.<br />They want to make the divorce as painless as possible for the kids," the source says.
