Bozza - yes, you are I think.
Personally I don't think that when people are divorced they have to reveal details of their agendas to their ex-es. That's what divorce is - the separation of two lives that were once one.
I therefore think that contact arrangements need to be fixed, with pick-up/drop-off times that every party (including the children, if they are old enough) agree too, and not changed. Though I do think it is good to plan to have an annual review of arrangements - every September, in our case, when we learn what our stepsons' school timetable for the year will be.