There are also people online who say they use just a single camera but mount it further back so it covers the whole back seat. I’m not sure how well you’d be able to see the kids if you did this though
I’m just going to use two mirrors above their seat, can still see both in my rear view mirror
Have you had a look at car cameras instead? I know they are much more expensive but you can get dual ones so they would have separate cameras in the back on each child but show up on one screen in the front for you