Help with what to do?

My ex had custody of my children for christmas in that period he called my son fat and stupid n retarded etc. Than he choked him in an argument and put him in arm bars on two occasions. He also taught them how to break toes and got my youngest son to do this to my husband who got tendon tears. The police interviewed him today and can not prove without reasonable doubt that this happened as it's my son's word against his. What do I do now... The court order says in a few weeks that he is to visit his father again with his little brother. If I do not send them than I am in breach of the order a criminal thing. All the officer could tell me that this will now be handed to child services to look at and I will be as looked into as him. WHAT TH?? DID I DO? Anyway my son will be 14 next week and my other son is 11 and I live in QLD Australia....any advice appreciated.