Sad father missing his children

I have two kids boy and girl. I was taking to court by my girl friend who is the mother of my kids for child support, she was granted from me to pay 120 a month.

At that time I had a good job, but as thing go wrong without your knowledge I was laid off. Now I find myself out of work, unemployment is no more and I have my mother helping to send half of what I was requested to pay, she is on a tight budget herself, but willing to help me.
Now my mother has payed alot of money, so my children can visit me from Florida, but I now find out that the mother is not letting them come,even though she agreed to before tickets were bought.

Her statement is that she is applying to walfare,my mother is going to loose that money because they are non-refundable. The kids do not live with their mother, but with their grand-mother for the past 7 years, she was recently married and not caring for them, my kids are age 16 and 14 she says she is not getting any money though my mother is sending it to the Florida Disbursement Unit...she claims she and her new husband are unemployed and they need goverment help...this person is very selfish......I do not know what to...I want to see my kids. She has told the kids that the judge said they are not to visit me, because she is going to be arrested...I don't know if this is true..can a judge state this even if I am sending some child support....??

Please help...