I'd say that having a biological child with your foreign wife goes a long way to proving intent and that the relationship is real. Or you can bring lots of photos and correspondence.....I hear that works as well.
This was my third foreign wife interview at a US embassy in my life and only two questions were asked. Both directed to my wife. 1) Do you know how many times your husband has been married? and 2) Where do you plan on living in the USA?
Thankfully she knew both.