The toning does, indeed, add a very appreciated nostalgia to the scene. I agree with you in preferring this shot to your entry. The vignette on the other was a bit overbearing to me, and it added a weight that I wouldn't associate with the scene. This shot leaves that lightness of being intact, much to its benefit.
Really love this... and learned something (as I often do viewing your images) by thinking through what I believe your execution and equipment produced.
It has a very 50s 'boys of summer' type feel to it.
I like the juxtaposition of the frenetically exercising boy with the calmly walking one - sort of ' Okay, enough of that nonsense'. The sepia tones are nice.