You are thinking the same thing I am. It is a very difficult thing to manage in group care, as you know.
The things you can do to help your own child are not things that can be done with other people's kids. It is made incredibly difficult when the parent does not want to see it, help with it and flat out denies it exists. My gut would want to help, but I would really think it through as to what effect it will have on the other kids and your own family's needs at this time.
This is one of those hard choices because he may not actually be able to help it but we still have the responsibility to keep everyone else safe first. It's tough.