Another vote for calling cps. As a teacher I work pretty closely with cps, especially when I was doing early intervention. It is a scary call to make but necessary in this case. There are lots of horror stories out there But they want what is best for the kids. Often those stories have hidden information that was vital to the decisions made by cps. In my state they always prefer the children go to a family member if they need to be removed. If you make the call and you would like custody I would make that very clear to the case worker. I know of many cases where the grandparents act as the foster parents and then dependent on the outcome adopt the children. My aunt has gone through this process (cousin has mental health issues as well as cognitive impairments and the father who is now deceased was an abusive heroin addict)...they were a wonderful resource for my aunt to navigate taking on two young children and later adopting them.

Best of luck to you