My 14 year old daughter and 12 year old daughter have both expressed a desire to not return to their father's house for visitation. My 14 year old expressed this to him to which her father stated he would contact his lawyer if she was not at his house on the specified custody day.
Family Law Attorney
In the State of Missouri, judges have the ultimate discretion. The statues state that children have a say when they get older, usually around 14. If your daughters' have expressed a strong preference, when you file your Motion to Modity the Judge will appoint a Guardian ad Litem. Your daughters will have to express their preference to the Guardian ad Litem.
Child Custody Lawyer
Custodial preference of a child is one of the factors that a court considers in awarding parenting time (viisitation), but not the only factor. The Court would want to know what is going on at the father's home, and why the kids do not want to return. The what and the why would be very important, on the final outcome. Probably time to visit with your attorney.