Really nice. Some small things I noticed:
The quick cuts at the very beginning just didn't work at all for me. I had no idea what was going on, and it felt like a mistake in editing. I'd hold those shots out quite a bit longer just before the kid starts play-fighting.
When he goes into the imaginary warzone, the color correction is very weird. I like the idea of changing the colors, but it could have been a nicer adjustment. Seems like you just boosted blues in the black range and maybe a bit in the mids, and I think I know what you MEANT by it, but it still looked off. Of course, good color correction is a very hard thing to do properly without detracting from the storyline too much... But if it were me, I would have shot the imaginary warzone sequence on a different, more overcast day, and brought out the fog machines for some rolling mist. Then shooting at maybe 45 fps, ala Saving Private Ryan. Combined with a very, very slight bluish or greenish tint, I think you would've been closer to the look you were trying to acheive.
I loved the slow-motion at the end. All very well composed shots. Did you use one lens for the entire shoot, or more than one?