Dorothea. The conversation will be great and she thinks outside the box. Also, John would be overwhelmed with guilt at getting shipwrecked, Nancy would be blaming everyone but herself at being shipwrecked, and Susan would be worrying about the other vessel and its crew. Dorothea and Dick have been shipwrecked (if you count a sailing sledge and I bloody well do) and managed to find shelter very competently. Also, if there were hostile people about, five minutes exposure to Dorothea and they won't be hostile - who in the entire canon has got an apology out of the GA?