Okay, so your rooster is not a pure Cochin. I honestly don't think he's got any Cochin in him at all based on his traits. He looks more to me like a d'Uccle mix, and likely not a first generation mix based on his traits. He is the source of the little crests, the beards, and the extra toes on the chicks.
The smokey pearl has light shanks and so does the rooster, but that being a sexlinked dominant trait, the rooster could be split for it. If he is the only rooster, then he would have to be as otherwise you would not see dark-shanked chicks at all. So about half of his daughters should have dark shanks like you're seeing, with the other half having light shanks like their brothers. This means you would not be able to sex all of his chicks this way, but you can be pretty confident that any dark-shanked chicks like those pictured are female.
White Cochins are white due to a different gene than the smokey pearl, recessive white, so a White Cochin's offspring would not be white unless bred to another white bird. The smokey pearl is white because of the dominant white gene, which lets flecks of black through, and that gene will also let red pigment leak through as you're seeing in some of the chicks. The only other bird I see in your pictures that could produce similar chicks is the red hen with white tail feathers. She also has the dominant white gene, and, when bred to a mostly black rooster like the one pictured, could produce chicks that are mostly white with black flecks and some red leaking through. So either the smokey pearl or the red hen is the mother if those are all of the possible mothers pictured.
As for what to expect from those chicks, I would expect either white with black flecks or white with black flecks and red patches. The male with the red starting to emerge especially is likely to develop a bit more of that red as he matures, mostly in his hackle, shoulder, and saddle area. Pullets that develop red are more likely to develop it more spread out, possibly concentrated to the chest if at all.