What can I do about unlawful visitation and interference?

If you have a current parenting plan that allows you visitation, you need to file a motion to enforce that parenting plan. The courts will insist that she follows the parenting plan or be held accountable. 

If she does not comply immediately with the court's order to enforce the order, you need to file a petition to hold her in indirect contempt of court. This will allow the court to go so far as to issue a body attachment (that's a civil arrest warrant) unless she cooperates with the ordered visitation. 

Finally, due to her intransigence, you will likely need to file a motion to modify the visitation schedule so that you can see your children more often and allow you to be the parent who takes the children to school. In such a case, a Guardian Ad Litem will likely be appointed to find out why your ex-wife is not taking the children to school or allowing you your court-ordered visitation. There are likely additional disturbing details that need to be addressed as well.

I am sorry that you and your children are going through this. 

Generally, your ex-wife cannot refuse to comply with a court order for parenting time or visitation because she does not agree with it. You should keep a log of each missed exchange, including dates, times, messages, and witnesses. Continue to communicate in writing as calmly as possible. If there is no court order or the order is ambiguous, it may be more difficult to enforce a specific schedule until the court enters or clarifies one. A parent’s refusal to send children to school may raise separate concerns, especially if children are required to attend school under state law.

You may be able to file a motion to enforce parenting time, a contempt petition, or an emergency motion if the children's safety, schooling, or well-being is jeopardized, depending on your situation. You can also call the school to confirm attendance records and talk to a family law attorney about what your best next step is in your state. 

If there is a court order and she violated it, you can file petition for rule to show cause. if there is no order you need to file a motion.