Often these first-right-of-refusal clauses lack the specificity necessary for them to work cleanly. It sounds like this is the case with your parenting agreement. You have a choice, either wrestle over it or choose to reject or accept what has been offered. If you wrestle, you can expect the primary outcome to be the fight itself.
MY FRoR clause applies only to overnights. If I'm staying out late, I don't need to take the awkward step of involving my ex. If I'm traveling, she gets the option. This has worked well for us.