Starting a Children's Story

I’ve just started a new story, so I decided to blog about the process—from beginning to end, wherever that might be.
When I decided to write this story I already knew I wanted to write for the same audience I’d just finished writing for: 8-10 year olds. And I knew I was going to submit it to the same publisher as the last one, so that gave me a strong structure to work within. I know this story is going to be around 1600 words, and that it will have around 16 chapters of a thousand words each. This may seem formulaic, but in fact it allows me to stop worrying about length and structure so I can focus on things like character and plot development.
I also knew I wanted to write about kids and the natural world again, and the place I know best in the world is Vancouver Island, so I decided to set it there, at least in my brain, even if I don’t name it specifically.
I’ve long had a passion for sea otters, so I knew they were going to figure in the book, and I thought this time I’d write about a girl as my main character, but that was all I knew.
As you know, a lot of the writing process takes place away from the computer or notebook. I started thinking about this story: what could happen, who it might happen to, what would happen then, how would the character get out of that situation? I thought of the advice my friend Alex gave me: put your character in a bad situation, make it worse, then make it better. So I put my character in conflict with her family, made the whole family get in trouble because of it, then made the main character find a way to make it better.
So far all of this plotting took place in my head. I like to work in my head for a while until I get a sense of where the story might go, then my next step is to sit down and write a chapter outline. And I do mean a detailed outline. The whole story is 16000 words or so long, and the chapter outline is 4000 words. I think this is a good ratio, because it means I have captured all the details of what is happening, but left room to dramatize the action.
So that’s where I’m at now. I’ll read over the outline to see if it makes sense, if the character’s motivations are clear, and if I can improve it anywhere by adding more danger or drama. The next step is to write out the first chapter to see if I can find the voice of the main character. Wish me luck.