If both parents are citizens, then the dual citizenship of the parents is of no concern. The concern is when one of the parents is not a citizen at all and might conceivably have NO loyalty to the nation.
Is a child born in a foreign land to a naturalized U.S. citizen and a non-citizen "natural born"? I don't believe that is what our Founders intended.
I doubt they thought much about it at all, since wives were universally considered to adopt their husband's nationality. So if the father was a US citizen, so would be his children by the operation of natural law, regardless of where they were born. Conversely if the mother were a US citizen and had married a foreigner, her children would inherit the citizenship of the father also by natural law.
In other words in the time of the founders, one need not consider the situation of mixed nationality married couples. This is a modern development and one that we must adapt to.
With the modern day acceptance of the equality of the sexes before the law, and where wives no longer adopt the nationality of their husbands, women as well as men must be able to bequeath their nationality to their children by the operation of natural law. It's not 1765 any more.