Array modifier on parent and all of its children I have a parent with a lot of children. I want to use an array modifier on the whole lot of them, including the parent, but, when I add an array modifier to the parent, only it gets duplicated.

One sort-of-solution I found is to Duplicate Link the parent along with its children, but this requires fiddly manual positioning that I'd like to avoid, and I also think this would make it difficult to add a child. The other solution I found is to add an array modifier to the parent and every single child; although this method does what I want in theory, it's still a lot of clicking.
Create your parent object, then create one child. copy the array from the parent to the child Ctrl-L. next take the child and add drivers to all of the parameters in the array modifier that you want to auto update. now copy the drivers and array modifiers onto all  of the other children. Done!

Using drivers is tricky, Here are some tutorials:

https://www.youtube.com/watch?v=o4qYHNA_x4Q

https://www.youtube.com/watch?v=ajMAvKRCTBg

How to copy drivers onto multiple objects