It would be the easiest if they were dead. All that had to be done was to find their bodies and bring them home to Jennie.
If it was the second or third possibility, the mission was to find Edmund and Salem, whether they were hiding voluntarily or involuntarily. It would be considered done when they were brought back to the United States.
Hence, Harrison looked at the direct family members on either side of the table and asked, "Who among you wants to volunteer to go to Oskia and help Jennie