It's a real double edged sword, IMO...

On one hand a CPS intervention is intended to provide preemptive protection for children & if deemed necessary & performed sensitively by staff with high levels of both common sense and diligence, is likely a good thing.

On the other, it is very potentially intrusive & upsetting to both a parent with MI and to the child. If enacted, there should be reasonable grounds to do so & there must be no presumption of risk without diligent, but sensitive investigation. Sadly, these are characteristics that I don't automatically associate with large, impersonal bureaucracies. If seeking assistance for a mental illness is to be a trigger for something like a CPS intervention, then it must be done with the well being & rights of all affected being respected, as well as with an eye to preemptive protection.