Thanks for posting the color pic; that’s the one I wanted to post up (I just got done downloading everything from photobucket & am in process of setting up at the other image hosting site)
The two younger boys in your first pic, and older girl in your second pic also appear on page 54 of Mark’s book, in the pic with the white man and woman.
Here we can see the younger of the two boys face.
And the older boy next to him has striped swim trunks, same as in the first and second pics you posted.
the boys and girls are the same kids as in the first and second pic, because the swimsuits match.
Right, and so it follows that Mrs Baker, Ruth's mother, is the woman looking over Mr Baker's shoulder, who has his hands on MARK'S shoulders.