All you can do is try. I've never had any problems with my bigger girls when integrating other birds, though mine are light breeds and they are very docile (Houdans and NZ/British Araucana). I'd try mixing them free range (but supervised) at first so that they have lots of space to get away and make sure the Silkies can see round their topknots. You'll have to judge by your bigger birds reactions over time as to whether you think your Silkies will be safe. Your little cockerel is far too young yet to take on the older birds if they decide to be mean. Just remember that a Silkie's top knot will make them sitting ducks when it comes to predators and they are often better confined to a run.
