[Fl, USA] Coparent backing out of schedule change

Location: Fl

Ex husband has court ordered every other weekend time sharing with our two children. We do not have a further detailed parenting plan yet as our divorce isn’t finalized. For context: he is only allowed to communicate with me via a court ordered parenting app which is admissible in court. I asked for a weekend switch. He agreed, which I have in text on our app. I go ahead and immediately make plans according to the agreed upon switch, including a significant get together for our middle schooler and her friends before their first dance (dad would not take her to this so for her to be included it would need to be on my weekend), as well as a friend spending non refundable money on plans for my newly updated weekend without the kids for both of us, based on me committing to those days with them.

Twenty four hours later I read a message from him rescinding the agreement to switch because he forgot about plans he made with the kids for one of those weekends. I tell him I’m already committed to plans. He tells me I’ll need to change my schedule then. I tell him I can’t do that and that my plans also include an event that’s important to our daughter, and that it’s not my responsibility to be the one to change my schedule because of his oversight. He rebuts. Now we are deadlocked.

Who would the courts/law enforcement side with in this case, should we continue to not reach an agreement? And if the law is on my side here, what should I do or who should I contact prior to provide proof that the switch is enforceable, to avoid this escalating to one of us calling the police on each other for withholding the kids?