Not bad, John but I think you focused on the lady's leather jacket...both the faces of the boy and the lady are soft...Is that intentional?
1/350sec at ISO500 and f/11.0 with a 600mm focal length seems less than ideal. The good news is that depth of field increases with focus distance, so with far-off subjects, you can get sufficient depth of field with wide apertures.
That said, I suspect you were wide-open (2x teleconverter on an f/5.6 at 300mm lens). Most of those 70/75-300mm lenses are fairly soft, but I think you can improve your results a bit by trading some noise for shutter speed. Try ISO1250 and 1/800sec-1/1000sec and see if it sharpens up.
In terms of focus accuracy, the woman looks sharp below the waist, but not above, so I suspect you back-focused a little. Misses are inevitable when manually focusing long lenses, but practice pays off.
Lex,
Thanks for the comments and suggestions and you are right about being wide open on the lens, it was a series of hit or misses on that day. My BIF were mainly misses but I did get one good shot of a seagull, missed on about five shots of some geese coming in for a landing.
That woman's stride is quite striking, John. Did you happen to catch her further on without the boy alongside? I think she and her shadow in mono might be interesting.
Greg has precisely expressed my thoughts. Had the woman been isolated, and the shot converted to B&W, I think it would be a keeper. The boy and the colors dilute the impact in my view. I'm curious to see what your ongoing experience will be with the 2x. Although I've seen impressive sharpness with various 2x TCs, my own experience is that compared to a 1.4x, they give up too much sharpness. I hope your experience is different.