That is funny about their hiding.
As I've read, Khakis and Runners are already quite skittish birds--seldom can become hand tamed (though some can succeed somewhat, with effort).
I wouldn't expect these birds, esp. as adults to ever really come around. If I were you, I would breed the Khaki pair to start a family if you can. Get a Muscovy hen as a natural mother--since you like the 'natural' side too! She will set the eggs, if she has good mothering instinct.
We will be getting 10-15 Campbells in the Spring--babies......
great luck to you, and I do hope that you are one of the lucky ones and your new babies really calm down for you--I am sure they will 'somewhat'...
happy new year, too!