This is really impressive.
The noteflight software does an impressive job rendering the sound, but I think this needs a live performer! (I'd volunteer but my piano is ten years out of tune and in another house.)
Of course you could also go and render the whole thing with Minecraft note blocks!
I totally agree. He has a bunch of compositions that I'm eagerly waiting for him to learn on piano. Unfortunately for me, his piano instructor is very disciplined about the order in which he assigns music to be learned, and it doesn't leave much time for extracurricular material.