Harry Potter has been a very big issue in many Catholic schools, including my own children's. I have seen good arguments on both sides. But it is naive to pretend that it has not been an issue.
It's no more teaching our kids satan-worship than other fanciful tales such as the Wizard of Oz or the C.S. Lewis books.
As a Catholic, you should seriously examine the content of the Wizard of OZ and the Narnia stories. I'm not saying that they are evil, but I would think that every caring parent will want to examine the contents for themselves. L. Frank Baum's story is weird and each book gets weirder. There's a good chance that they are harmless, but I wouldn't just assume so.
I don't assume so. That's why I have read them all before forming opinions.
This should answer your question about what the Wizard of Oz is about.