Wondering what my options are....desperate?

Here's the background story: I moved out of state in January of this year. I'm in my late 20s. My family (my mother, brother, and grandmother) did not approve of me moving across the country. They got extremely angry because I moved myself as well as my children due to a job transfer. Since then, they have threatened me by sending harassing e-mails. They said I was dead to them for taking my kids. They attempted to report my own vehicle as stolen, they will call my bank and try to pose as me, they have called the police stating that I am a drug user (which I have never touched drugs), and they tried to coerce my old property manager into lying and stating that I have written bad checks in the past (which is untrue). So...my question is this: I want to be left alone. They found out my new address and I fear for my safety as well as my children's. They have proven to be psychotic and I just want it to end. What can I do legally? Are my hands tied? Thanks.