yes he will mate with the hens if he is of cock-a-doodle-dooing age and provided your hens are ready to mate too (showing signs of stooping and egg laying). The chances of eggs being fertile are relative to how much mating has gone on. He will probably have a favourite, so her eggs will be best to hatch.
If you are using an Incubator to hatch them, then you can test fertility on day 7 via candling. Google this or search on here about it, it's literally shining a high powered light through the egg to reveal an embryo inside. If you are wanting to hatch some naturally, then you must wait until a hen goes broody. Some breeds don't go broody due to it being bred out, but silkies are good broodys and good mothers, and if you leave some eggs in her nest gradually over a few days then she will start to sit on them and raise them as her own, even if they are not. You should generally segregate (i think) a mother and her chicks from the rest of the flock- but not sure. Research this.
Thanks, Kelly.