I think calling them Mr and Mrs George Clooney is dreadful, personally. That etiquette dates from when married women were legally their partner's property. Amal Clooney is 39 and has achieved as much in her own right if not more than her heart-throb, coffee-loving actor husband.
I try to address cards to friends as they wish to be addressed, not how I wish to address them.
I made it clear when I married that I wasn't changing my name but if older rellies prefer to address Christmas cards in (non-existent) married names then I am not going to be rude to them - and I notice that over the years, they've changed.