Warbler, I echo what Tyrphanax said. They both need help. And as I work for behavioral health focused on children so young, I can tell you that these children need help, even the little girl. People often think, "Well, the kids are so young and won't remember anything," particularly with children as young as the girl was. But children are affected for their lives by witnessing such events. Even if they don't consciously remember any events, it alters their perception of the world during these crucial times of cognitive development: the way we all see things stems from before you can even remember! Honestly, I would recommend calling CPS. The police are legally obligated to do so in a situation like this (at least in AZ, but I assume in NJ as well). But really I'd suggest you are morally obligated to do so. That doesn't guarantee the kids will even be taken away, but rather that they will determine if the report merits an investigation. If so, an investigation may show removal is not warranted. But if it is, the children will be safer while Mom gets her act even more together (such as by leaving Dad). It may seem harsh, but these children are defenseless against an abusive father, and if their mother cannot keep them safe, someone else needs to while things get sorted out.

Hope this helps.