We all should know that magic is nothing more but non sense. Especially that kind of magic anyways.
I have read most of the books and seen to my knowledge, all of the movies. There is NOTHING wrong with none of it.
If you don't want them to read the stuff. Simple. Spend time with them doing something else, and then bingo. You are good to go.
I know plenty of kids who read and watch the movies, and they are just fine.
I know a few in fact, who went from not reading at all or not to well, to reading amazingly well from those books.
I agree, that the series needs to end soon, just for the simple fact, that after a while, it does become boring.