My ex files taxes on one of our kids and isn't up to date on his childsupport?

My ex doesn't pay his childsupport at all says he isn't going to either being he has a savings account for them but I don't have access to this account, and being he get's them half and half through the week, not to mention he doesn't follow what is in the dicorce papers, he is supposed to send them home on his days when he has to work, but he lies and takes them to someone else, which I find out later he did this, he also files taxes on one of our kids, head of house hold and earned income to, it staes in the divorce papers that he can file on one of them, but it aslo has a statement saying that he has to be up to date on his support as well, I talked to my lawyer and he told me that I would have to take it back to court, I don't want to put the kids through that again so what can I do. Help!