Critical situation needs addressed...please help.?

Here's the scenario: Father and mother have joint custody, with the mother being the primary and residential custodian. There are no court orders regarding visitation. The parents have always 'worked' it out, without any significant problems ever having arised. The father picks them up every other weekend during the school year and every weekend during the summer. One day, their 10 year old child confides in the mother. She explains to her mom that her 17 year old cousin (her father's nephew), has kissed her with his tongue when no one was around. Her younger and 9 year old sister is witness to the incident. The mother immediately calls the father, explaining what his sister's son has done to their daughter and makes the request (as if it should even be said), that he never again take their daughter to be anywhere near or around the boy. The mother makes the umption that he will more than willingly comply and perhaps even beat the boy up! His response...silence. Shock? Perhaps...but I'm afraid this isn't the case. Allow me to continue. The mother then calls social services immediately, explaining what has happened, only to be told that there is little, if anything that could be done in the way of prosecution, as the boy is 17 and it is an instance involving only the tongue kissing. Already being a given that she will call a counselor after speaking with social services, the man from social services, himself, explains that counseling is the other option. Naturally and afterward, the mother calls the counselor, who is very much in support of nurturing the daughter's emotional health amidst what has happened to her. A few short days later, the counselor visits with the mother and both daughters. All seems to be going well at this point...all things considered. Some two to three months later, the daughter again confides in her mother, explaining that her father has continued to take her around this boy and that it makes her extremely uncomfortable. The mother then calls back the same counselor, explaining what has happened where the father is concerned. The counselor states that it would be good for the daughter and her sister (as the sister shares these same feelings), to tell their father themselves (as opposed to coming from the mother), that they do not wish to go with him, for fear that he will take them around this boy. The counselor offers no further advice at this point. The mother ponders the thought awhile, but just doesn't feel quite right about it. You see, perhaps this would bode well, if the daughters were not in fear of making their father angry. In this case, the girls are afraid to tell him anything contrary, as he is emotionally controlling, actually, and this has everything to do with why the mother ever left him to begin with some several years ago. A little later in the day, after having spoken with the counselor, another counselor from the same place, who has talked with the daughter at shool that day, says that this boy (who is now 18), needs to have a restraining order (epo) placed against him. The mother cries, as she is relieved to know that something CAN be done. To make the long story short, what needs to happen...what can be done...what should be done...concerning the father and his own victimization of their daughter? What on earth needs to happen here? What can be done to him? What should be done? I hope that I have explained things well enough and I sincerely appreciate your thoughtfulness to answer such a serious question. Thank you.