As habitual heathen, we did not do much for Christmas other than treat it as a 2 week party break. But then the first little nipper came along and well, when ya got kids, it's kind of very unfair not to do the santa claus, tree, lights etc bit. And so it continues. We like it, it is fun. But I once was told this and still remember this quote:
People really act weird at Christmas time! What other time of year do you sit in front of a dead tree in the living room and eat nuts and sweets out of your socks?But the card at work thing, each workplace will be different. I don't do it myself and in 30 years and umpteen different places I have worked here, I have never experienced the 'it's expected' thing. But I do know (because of DD, ex DW, DW & DS) that there are many places, like Jewlz's workplace that do expect it sort of. Not sure how how I'd handle it but I'd probably do it so as not to be the bah humbugger.
axial tilt is the reason for the season! 
BRILLIANT!!!
The thing is, it's VERY difficult to find cards without the word 'Christmas' on them in the UK!
I've always managed to find ones that just have a picture/image of santa, reindeer, a bird etc with just Season's Greetings on the inside.