You need to contact a lawyer for an in person meeting immediately.  There are options which really need to be discussed in person not on an open forum where things can be taken too literally or even worse, out of context.  You are in a very difficult position; keep in mind:

First, if there is no court action filed or pending, you have equal rights to visitation, access, possession, etc.  However, if you trespass, disturb the peace, etc. in getting possession of the kids, you may be criminally charged.  

Second, if she has crossed a state line or has filed for any court protection where she lives, you may be violating a court order, even if you do not know it exists.  While you can not be held in contempt for violating an order you are not aware of, you can expect the local law enforcement to "enforce" the order that has been signed.

The proper method is to file for a divorce where you live or where you think she lives and ask for a WRIT OF ATTACHMENT on the kids.  She will have to respond and if there are orders elsewhere, she would have to make that known at the first hearing.

A writ of attachment is an order to the sheriff to go get the kids and bring them to the court.  Expect to have an immediate hearing once the kids are located.  The Judge will need to decide who will have temporary custody.  Once attached the kids are wards of the court/sheriff until the court rules, so there is little time to prepare.  

Again, you need to get a face to face discussion with an experienced and aggressive attorney immediately.  If you are in Collin or Dallas Counties, let me know, I would be happy to set you an appointment to discuss this more thoroughly.

Roy L. Reeves - Reeves Law Firm, P.C.

www.planoattorney.net