OP...
I'm.going to say this in a purposeful way, I know it will upset people.
Any advice you get from anyone with a vested interested in giving that advice should be covered in huge pinches of salt.
Take that link posted above by Windy
The whole article was written by a psychologist that was educated in the late 70s... Imagine someone of 65years old now and imagine their attitude to tech and screens and how most of that generation blindly dismiss them and hate them and think kids should be out on bikes like they used too. It colours their view of the modern world.
No imagine an educational professional who writes books. Of course they're going to push whatever sells books. Parents of kids that are perfectly fine and dandy aren't buying parenting books, the parents of kids with issues are buying them and looking for a reason that their kid has issues. So when a study of 200 kids shows a minor detrimental effect of screens, they'll latch on to that and push that as the cause.
So the researchers get paid to find a cause, they find it. Other people who are already biased read the research and parrot it because they can't do their own research. That parroting gets further repeated in newspapers and online and before you know it something is demonized.
Bit like how that one research paper posted by an idiot has led to anti vaccination movements.
So, I'd recommend, you ignore the research, ignore this thread and Every single poster on it. Listen to your children.
If they're happy, healthy, meeting the educational expectation and being active and playful, then they're doing just fine, and that's all that matters.