The 16 year old nephew should get Burberry Brit or London IMO. Or something with lavender to calm him down from being hyper.
Rochas Man would be good for nephew #2. And I do think John Varvatos would fit him, based on your description.
Or maybe something peppery? Bang maybe?
I personally wouldn't buy them huge sillage monsters.
And I don't want to offend you, but Christmas is quite far away, LOL.