I think singing round the piano was killed by people starting to watch tele. I remember cycling to visit an uncle who had just got one and we watched one programme after another. I suppose that would be mid/ late 50s.
I certainly can remember family parties where we went round the room and every one did a turn.
Uncle Alf sang 'Seated one day at the Organ' or recited 'The touch of the Masters Hand' (a poem about an old violin).
Uncle Cliff pretended that his performing flea had escaped (but when he finally caught it it wasn't his flea at all)
The aunts played songs for us to sing (it was the girls who had had piano lessons)
The children went outside and invented and rehearsed little plays.
At the tea table we sang a song for everyone there - K-k-k Katie for my mother, Hang on the bell Nellie, Little old lady passing by for my grandma etc.
The song that evokes those Christmases most is Loves Old Sweet Song.