My opinion, I don't think it has any Silkie in it, there's no fuzz anywhere. Yes Silkies have five toes, but as Silkiechicken said, so do several other breeds.
Langshans don't have 5 toes, so there's an elimination.
Houdans have 5, but no leg feathers.
Faverolles do have 5 toes and feathered legs, and come in black (unofficially.)
Sultans have 5 toes, feathered legs, NO crest (even though they have a poofy head), and can come in black (unofficially.) There's a maybe!
I think it is a standard, and a hen. That's all the research I have, sorry *haha* If you would like pictures of these breeds, check out feathersite.com. And
http://www.mypetchicken.com/chickenBreeds.aspx has nicely organized info of each breed. Tell your son we are all proud of him, and congrats on his new buddy!