There's little doubt the dark boy is the one standing with Barack Obama and Ruth, but he isn't Mark, and we are back at the beginning. Who that boy is shown with Mark from the original book cover, I have no idea. You might need to allow for it to be a composition. He looks too much like the child wearing the University of Hawaii T Shirt to be anyone else...
The child Stanley Ann and the Kenya student didn't have in August 1961, bears a resemblance to the boy Mark names David - who would need to have been born some two years after Mark, as the son of Barack and Ruth. I'm leaving it there, I need a strong coffee...or something.
Ear shape of left hand boy, and that of the boy in the white dress shirt are different.
(White dress shirt boy is the right hand pic of the second row)