You are actually asking more than one question. (1) You were ordered by a judge to follow the judge's orders. If you don't follow the court orders, you can be held in contempt of court by the judge. The "over the age of 12" is irrelevant. A child does not get to make "visitation decisions" until they turn 18. I receive questions similar to yours often about "visitation over the age of 12" & I have no idea where people get the idea that children get to decide things when they turn 12. You can read the TX Family Code on-line but no where does it state that a 12 year old (or older) gets to made decisions regarding their visitation.
2. If their father is "acting weird" perhaps a modification of his visitation is in order. You need to talk to a family law attorney. There are many on this website. So look around and meet with one in person.