If a major event was happening in your family, hatches, matches, dispatches, etc would you expect the organiser to ask you first if day was ok before sending out invites? i would - just did a big family day out for 20 for Aunt's 80th, and asked all parties beforehand to send an email with dates that were non-negotiable so that I could plan event. Everyone co-operated - day went well. Now, my sibling, has planned a communion and not asked anyone beforehand and is pissed off that we, and others, can't attend. AIBU or AIHighly and perhaps too Overorganised??