The frum community needs to get involved. ACS reporting is mandatory for people in the health professions and social workers who are aware of a problem. If you are merely a neighbor who notes things going on, perhaps you can get your local shul involved, a Rov and Rebbetzin, Bikur Cholim, etc. to see how they can help.
Find out who their family members are and if due to their seeming lack of interest it becomes NECESSARY, let it “slip” that you heard that someone has been talking about calling in Child Services. That sometimes spurs errant family to get involved where they have made themselves “nisht visindig” prior to this, expecting other people to pick up the slack. And if they only do it because of fear of what other people might say (I have seen that, too), it is still probably better than social services getting involved.