Take a read through this http://us.imdb.com/Bio?Bullock, Sandra and see what you think. While it makes no reference to children, it makes a few references to her stance on Marriage. Those being what they are, I'm hard pressed to think she would have had a son.
Add in on top of that a google search for Sandra Bolluck children coming up with nothing.
Examine the shadow line in her chin and the lack of a shadow line on his. She's 5'8, how tall is he? If she was wearing heels, that'd put him a few inches taller.
I'd say call his bluff and ask for another picture.
