In my access agreement, exH gets to se them every other weekend, Friday to Sunday. This is called 'ordinary weekend schedule'.
Mothers day they spend with me, Fathers day they spend with him. My birthday they are with me, his b-day they are with him if he wants. These are 'special days'.
We each get to have a period of 12 days in the summer with them and can take them for a break anywhere in the country, or out of the country with advance notice. We alternate years for first choice of when the 12 days will be taken. This is 'vacation time'.
We alternate Easter -- he gets them one year from Holy Thurs to Easter Sun p.m. and I get them the next year. I insisted on always having them for Christmas so he gets Christmas eve (morning to late evening) and also New Years eve. These religious and calendar holidays are called 'holidays'.
They spend half the school Christmas break with me and half with him.
For 'holidays' and 'special days', the 'weekend schedule' is put on hold, same goes for 'special days'. The summer 'vacation' time is not allowed to run over the other parent's weekend, hence 12 days. Other school breaks I have the children.
In addition, there are provisions for going to family funerals, weddings and other significant celebrations. He and I are both obliged to ask each other first if any babysitting of the children is necessary -- if I am going to be out for 3 or more hours I have to ask him to take care of them and vice versa while they are with him. For their birthdays, there is a provision that the other parent will be invited and welcomed to celebrate on the b-day at whatever residence the child is in at the time. In the case of parties held for the child outside the home, the parent who doesn't have the children at the time is invited and made welcome there too.
The DCs don't go to see their father on week nights, but he is allowed to call them any time and talk. He hardly ever does.
If you break the occasions down into categories, you might be able to come up with a compromise that looks reasonable and that causes the least possible disruption to the child's sense of belonging somewhere.