You sound like me creating holidays. July 4th is the Summer holiday my Sims celebrate and I too separate Christmas Eve and Christmas Day. Father Winter comes to visit on Christmas Eve and the grand meal is on Christmas Day.
I also researched Pagan holidays and set them in some of my households.
Yes, activities most definitely need an update. I love how they gave us the ability to allow our Sims to celebrate the holidays we wanted them to - THAT was diversity done right. No forcing anything on anyone - completely up to us what they celebrate. They just need to open up more activities to make them feel closer to what they are.
