Though I understand that the modern trend is to look towards the technology for an answer, you must also not forget to look at the subject.
Sharpness, or the appearance of sharpness in an image is strongly linked to contrast (or more accurately, acutance). Hence the terms 'hard light' and 'soft light' because it really does make a difference.
Now all the images on this page where there is sunlight you have placed the kids in the shadow and pointed the camera into the direction of the light. This reduces the contrast in your subject considerably (and adds lens flare), it also decreases the levels of light you have to work with. With "Jack", for instance, his face is in shadow because the main diffuse light is from behind.
Try shooting a couple where the light is behind your shoulder and illuminating the subject rather that behind the subject so you're shooting into the shadows. See the difference.
EDIT: Here is the last shot you posted, as an example. See how you're pointing the camera into the direction of the light and placing your subjects into the shadow. You already have your subjects lit by the lowest levels of light and contrast. You are also committing yourself to bigger adjustments in your editing software inevitably increasing noise. I also can't help but notice that in editing you've recovered the detail in the sunlight parts of the image rather than giving the best renditioning of the subjects. With more careful subject placement the overblown highlights wouldn't be there so why edit you photo to them at the expense of the subject?
Original:
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Edited more for the subject:
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