It would be different if BOTH parents were taking him, temporarily, overseas while they served as missionaries or workers for the USA government or corporations.
If when he is 18, he decides to join his mother and stepfather in Egypt, then let him.
If the Egyptian were his natural father, my position might be different. My judgment is based on his having both natural parents white US natural born citizens.
This is different from the Elian case, but of course La Reno decided that one wrongly too, for different reasons.