One of the things I liked best about this was the portrait-lore--how all of it worked, Snape being pulled to the RoR, then being able to roam through the castles, and out into the world at large--travelling and learning languages.
I suppose that the infidelity of this story is Harry's failing Snape, not Ginny--that's how I took it at least, although he did have that little fling in NY. Sort of a biblical infidelity, when you get down to it--no vows were broken except for interior ones of conscience.
I enjoyed getting to know Harry's children; it was strangely comforting to see their interactions with Snape. And the end was gratifying, finally, to see them get to touch each other and satisfy the longing of years. Well done!