Would it be wrong to say christmas?
No.
Absolutely not. Say Christmas, say Passover, say Ramadan, say Quanza…say whatever it is you celebrate.
It is very sad that you would even think this but I can see why you would in this day and age. It is important to remember that this country was founded on religious freedom and that includes Christianity. Don’t allow far left P.C. culture to cloud your thinking. Be who you are and don’t be afraid to share that.
The context matters.
“We always go to the ballet at least once during winter break, and again during spring break.” Makes better sense as you are using your school district’s official terms for those school breaks/vacations.
“We always have Christmas dinner at my aunt’s house.” Is a better choice when you are naming a specific holiday.
^ if you are talking about the season in general, it’s probably best to go general , but if it is in some way related to Christmas, then christmas time makes more sense.
I agree, if you are talking about “Winter Break” use that, instead of Christmas Break. But if you are getting presents for Christmas or like to help in your community around Christmas, then say that.