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The photo was made at ISO 100. When you move into shade, increase the ISO to 400 and the lens will be shooting at f/4 instead of f/2. On the 5D2, you could easily make a photo like that at ISO 800. I'd probably go to 1250 if I needed to.
That way you get more Depth of Field. The old master photojournalists loved to shoot 35 mm lenses and pre-focus and use small apertures (larger numbers) to get lots of DoF.
Also, the shot was at 1/200. There is not a lot of movement there, but even so, 1/200 is probably a good choice. However, you could drop down more with a 35 mm lens to, say, 1/125 and gain some depth of field there.