How can I write good, informative children's books for KDP without using wikipedia?!

I'm writing for a foreign Azn KDP market.

The niche I picked for my first three e-books is pretty much saturated by the looks of it.
I get fewer and fewer sales every day, and that can't be good. I need money.

Since I just cannot fathom romance, erotica and all that soapy shiz, I've decided to start cranking children's books.
The thing is, Azn doesn't accept content from wikipedia, and I wanted to write about animals and educational stuff. Where can I get the info without being accused of plagiarism?
Are there other themes that are good for children?

Also, does anyone know where I could get decent free images for kids? I'm too broke to pay for 'em, so they'd have to have a commercial CC license (or something similar).

Thank you so much!

ok, I'm not gonna be of any help, but I just have a question for you: how much do you have to write, in order to make a living out of it (+1500€/mo) ?
I read a bunch of those threads, and thought about doing something in my country, but I dunno if it's worth putting my current projects aside?

thanks in advance, mate!