You’re not breaking the law. Though you ARE being spiteful, and in this case the kids are being used. NOW…don’t think I’m coming down on you–because I’m not. I’ve been there too.
My suggestion is that (if it is possible for you) to take the children to school this week. Let her know you will do this for this week, but that she will have to make arrangements for the other weeks. Also tell her that if she pursues legal action, you have evidence of HER breeching the contract you have concerning visitation.
I assume your children are young since they are being driven to school. The children should not be allowed to decide if they want to come see you or not. They should be picked up on your visitation weekends…period. Remind her that joint custody means you communicate concerning any extracurricular activities beforehand (if the wording in your agreement states that–usually joint custody has something to that affect).
If she starts complying with the agreement you have, then you can be more amenable to ‘helping out’. Technically, time that is not your custodial time is on your ex. I was held STRICTLY to my agreement, but since my ex was the non-custodial parent, he decided when he would have them and if it didn’t work with his schedule-he would skip his nights. If I asked him to pick the kids up from afterschool activities on MY nights, I was often told no…that was my responsibility…and technically it was. So I often rearranged my schedule to do so.
You feel bad not helping your kids, but she does need to comply to the arrangement you have. You dont’ want to go back to court for breech if you can avoid it. I don’t see that a judge would rule in her favor based on the ‘joint custody’ verbeage of the agreement.
Just my advise. But you’re not breaking the law by saying no.