How would you feel if a family holiday (immediate family, 3 generations) was planned for dates when you and your DC wouldn't be able to attend, when it was booked for those dates knowing you wouldn't be able to attend, and the dates don't align with an anniversary or birthday or limited availability of the others in the group etc that mean the holiday must happen then?
I can only assume it was deemed unimportant that DC and I wouldn't be there for a holiday for the 'whole' family.