Yea, OP couldn't have picked worse companies for aggressive copyright protection.

I used to work at Disney, and was amazed that they’re so large that their companies sue each other. Disney is so litigious that it sues itself lol.

Thanks for your thoughts. To be honest, I have no idea.

But if I google "Coloring Pages Pokemon", for example, I find dozens/hundreds of websites that are not Pokemon, so to speak.

Doesn't make it legal. As a small site, I'm sure you won't draw the ire of some big companies, but if you start charging money, you'll likely get a cess and desist.