I am leaning towards runners but they don't walk as upright as other pictures I have seen or as upright as the runner we have now. They do sort of look brown in the sun but they aren't brown they are black. One has a yellow bib and some yellow around the sides of his beak but his feet are all black. The other doesn't. My sister has 2 khaki campbells and I have seen what those look like. These 2 are WAY darker then them. They are definitely black. I am interested to see what they look like in the next few weeks. I have 2 Pekins and a fawn & White runner so we will see who they turn out to look more like. I am sure I will post some pictures again as they grow up a little more and see if anyone has any different guesses then.
Will be interesting to see how they turn out :) You are right that Khakis are much lighter as ducklings than your two are (in mentioning Khakis I just meant to say that yours might not be solid coloured but may have a slight pencilled pattern to the feathers, like Khaki and Dark Campbells do). I had two that looked the same colour as your two and they both turned out dark chocolate coloured. They had (and still have) black bills and feet. But you are the one who can see your ducklings up close - it's not quite the same only seeing a photo online :) Having said that, here is a black duckling for comparison: