I still can't get over the fact that either Mom or Dad would let a 5 year old decide who they want to visit or not visit. Divorce or no divorce. So when Mom is taking the kids to Grandma, it is only if they (the kids) say OK? When the kid tells Dad they don't want to go to the doctor, he says OK? A five year old can pick out what color hair barrettes she wants to wear. What cereal to eat for breakfast if it's in the house. That's about it.
TexMom--all you can do is help Dad grow a pair of b@lls. Because if he had those, this never would have happened. Take the advice about reverting immediately to the court order and filing contempt when warranted. Google for legal self-help in your area, go to court websites, download forms, OK. But after you do all that--it's on Dad.