Honestly, I just read it, and as you said, it wasn't too bad or terrible. For the most part, it wasn't even written as blood?
Thought it's definitely implied. However, even then, it's just dried blood? Who hasn't had a bloody nose? Or in this case. . bloody wing? I mean, I understand, you guys might have a little bit against the inclusion of blood. But as far as standards and other things that have been posted before go. . this wasn't that bad. I mean, in reality, I've read other books meant for children, and the blood, if there was any, might've been worse than what @Lightscape_Ironwalker wrote.
Overall, not my story, not my vote, but that's just what I think. I mean, everything you've brought up is perfectly understandable and it is a quite valid point. But. . yeah. I'm a little biased as you might obviously know.
"You'll never get to where you're supposed to be if you stop to throw stones at every dog that barks." -Winston Churchill
Here's a gif to make everyone feel happy again-