Melania Trump became a naturalized US citizen before Barron William Trump, the youngest child, was born, however, prior to Congress changing the law, from 1790 to 1950, wives and children automatically became citizens of the country of the husband/father respectively. This fact is easily available at the Library of Congress, history of immigration and naturalization, therefore, according tot he US Constitution and the laws in place at that time, ALL of Trumps children would have been considered ‘natural born’ citizens at birth.
His older kids have Czech citizenship from the mom so unless you think dual citizens can be natural born citizens, they aren’t. If he had married a Russian I don’t think it would be complicated at all to understand why the person shouldn’t be president. That was pretty much the point of John Jay’s qualifier.