Ivana became a citizen in 1988. Donald Jr., Ivanka and Eric Trump were born several years prior. Melania Trump became a citizen in July of 2006, Baron was born the previous March. Only Tiffany (daughter of Marla Maples) would meet the Vattel definition of natural born.
I mention this because if Trump publicly embraces the Vattel argument, he'll surely get asked if he honestly believes the children he groomed to follow in his footsteps are not Natural Born Citizens. He'll need to have an answer.
Something for you to read..NBC is not limited to Vattel it goes back to the early republics.
http://www.freerepublic.com/focus/f-backroom/2512143/posts
Wonder how he’s gonna break that news to the kids...