Children's Book Writing

Anybody write a children's book and know about age levels and vocabulary?

I had John look at my first book, The Calamari Kid. He pointed out that many of the words I used would be beyond the age level of a kid who would read a story like that. (such as tentacles, unpredictable, scheduled, skeptical, sodden, doubloons, etc.)

When I was a kid, I liked to read books that were challenging and look up words I didn't know. I thought everyone did that. I hated books that were condescending.
I'm working on the sequel now, and I'd like to do it right.

This book is published on Kindle. While I read over it with him, I found a couple of typos. This in spite of the fact that I proofread this thing so many times that I could have sworn it was perfect.

The errors are small, and I have not been able to figure out how to correct them. Just a sentence missing a period and one letter wrong in a word. (says HIM, should say HIS). If you read my previous blog post about this publishing, you will see what a difficult time I had. It looks like the only way to edit the book is to edit the original file and re-upload it to replace the original. I'm scared to death I'll screw up the original. I only vaguely remember how it's done.

I have decided that the best thing for me to do is to get the sequel ready and when I upload it, I will be reminded of the process. Then I will hopefully be able to make the necessary adjustments to the original story.