If you are the biological mother of these kids and there are no court orders stating the children must reside within this state or within so many miles of both parents, then yes you may take your children anywhere you wish in the world. Assuming you are still in Texas and haven't filed for custody yet, be absolutely certain that in your custody papers there is a specific clause stating you have the right to decide where your children reside without regard to geographical location and insist the father pay roundtrip for the children to travel to see him. In the event of proven abuse, meaning you have filed charges on him and these charges can be verified, chances are you can win a case to have supervised visitation only. Also include the father is responsible for at least 50% of all school clothing and supplies. DO this as soon as you possibly can due to the fact that until custody is established, he can walk in and take these children with him from wherever they may be and there's not a thing you can do about it until you have court ordered custody established.
I do hope this helps even though it is a bit later than July.