That's funny, but it sounds like your drake has finally figured it out.
As far as what you should do, you have to decide for yourself. If it was me I would keep the drake you have and see what happens with the ducklings, how they lay, etc. and then make a decision. Worse case scenario you have...
It really depends. The new picture makes it clear that your drake isn't purebred khaki, but it is not as heavy as I thought, so maybe it's a cross with Welsh Harlequin or some other layer breed. How much his ducklings end up laying is something that only time will tell, but I bet they are still...
Khaki campbell ducklings should be a solid dark khaki color without eye stripes. I think your male is a cross because, as I said, he looks too heavy and his head is too green. Khakis should be light weight, and they should never have a low to the ground appearance. This is how a khaki campbell...
The drake is a mixed breed, definitely with some Rouen in him, and maybe Khaki or buff duck, too. You can tell this not only by his coloring (you are right about the green head, that is not right for a khaki) but also by his heavier, low to the ground build. That is why you are getting mixed...