Re: skin color blotches
Yes, the image is fairly small which makes it hard to say. I see two things that may be what you are talking about. One, is what appears to be strong sunlight coming through the trees in small spots. It appears on their faces, arms, etc. It's especially visible on the forearm of the older girl. The second are very small splotches (can barely make them out on this small thumbnail) that could be either (a) developing problems from the original image; (b) damage from storage; (c) noise/clutter from repeated scans.
For the sun spots, I would just use the clone brush set to color blend mode. Sample color from good skin and paint over the sun spot with a very low opacity. It may take a few strokes, but will eventually match.
For the other splotches, it depends on what we see from a larger or higher resolution image. It could be that the dust & scratches filter will work fine. Or, it may take more steps. But, we can offer more/better advise if you can post a larger image. Better yet, just post a small area from the whole, at full resolution.