As their mother it is her right and duty to protect her children. You will have your opportunity to appear before the court to answer the allegations that gave rise to the order of protection. Even if she says she is dropping it, unless you see something official from the court you should show up. If you don't show up, it will likely be put into place for a lot longer.
Defamation lawsuits are fact specific and hard to prove and win. Even if you win you will have to collect and that can be very hard to do.
Every legal matter is fact specific, and there are often nuances in every case. This is intended for comment only, and does not create an attorney client relationship.
The short answer is yes, you can sue someone for defamation of character. I would suggest that you look on an Avvo for attorneys that specialize in that area of law so that they can give you good solid legal advise.. Many of the Avvo attorneys offer free consultations and you should consult with one in your area. Good luck and hope this helps.
This probably involves both libel and slander. The legal requirements for each are complicated and the a discussion of the elements of each are beyond the scope of this forum. Even if you can find an attorney willing to take this case on you will find the proof very difficult and on the assumption you win collecting your winnings will be difficult.
This answer was provided as a courtesy to you and no attempt was made to establish any type of attorney/client relationship.
I agree with my colleagues. You would want to speak with a civil litigation attorney to sue for defamation. Also, you may want to consider retaining an attorney to defend you in the Injunction hearing because if the court were to believe what you say is a lie, then you will have an injunction entered against you which could effect different aspects of your life in the future. Best of luck.
This answer is for general informational purposes only and should not be relied upon for your particular case nor is it intended as legal advice. I have not reviewed your case nor have I met with you and the answer to this question does not in any manner whatsoever establish an attorney/client relationship.