Halle Berry, Olivier Martinez -- United Front for Halle's Kid ... Divorce Civilized

Halle Berry and Olivier Martinez telegraphed to all ... they're not at war.

The couple with dueling divorce petitions took Halle's daughter Nahla to a birthday party Saturday in the San Fernando Valley.

Olivier is still wearing his wedding ring, but we're told it does not signal a reconciliation. The divorce is still very much on, but civilized.