So, late review, but I want to say that this is, overall, excellent. My one complaint was with one of Marissa's reactions, namely to eating someone.
For a 7-year-old, it was a very adult reaction. It was how I'd imagine a young adult, like a 20 year old reacting to it. I feel a more childish reaction would be to wonder if she could just pick the person out of her poop, A-OK, then immediately move to grossing herself out at the thought of it.
Conversely, the children in the final chapter were handled very well, they acted their age. It was a great finish.
That was all for complaints, I just want to thank you for having younger giants, they're far too few I find.

Good stuff, thanks for sharing! 

Great story, I cannot believe I havn't read it. Your work is always amaizing. Cannot wait to read your next story. Hope there is another sequel.