They can DF you for anything they damn well like, and they don't have to justify it really. O.K, you can appeal, but you are on dodgy ground by then.
How exactly do you want to "celebrate" ? for years when active JW's we had all our JW family round for a slap up meal, lots of booze, and the odd present given, we never thought of that as wrong in any way. My JW mum always brought Christmas Crackers for the kids !
Of course, if you want to go the whole hog, have a Chrissy Tree festooned with baubles and lights and stuck up the arse of a fairy, etc etc then you may be in trouble.
I don't want to tempt them to have a go at me but, I have wondered what the hell they could do if I said I am not celebrating any festival, Christian or Pagan, I just like trees with a fairy on top this time of year.
I don't believe in Jesus or Pagan god's so I am not taking part in anything like that, whatever it looks like. Of course, I cannot tell them I don't believe in Jesus, that is instant Chop Chop !