Good morning CJ,
apologies for the delay in replying, I put your question to one of our Tour Managers who has done this trip many times, she has replied with -
During the day, dress is fairly casual. Christmas Eve and Boxing day I would recommend warm clothing as we will be outside much of the time during the day. Coat, scarf and gloves is advisable too.
Evenings tends to be more smart dress. For the gala dinner on the last night, men usually wear a suit and tie and some do too for Christmas day lunch.
Your break is fully booked with 47 fellow travellers, ages range from 53 to 77 and the male to female split is around 40/60.
I hope this helps,
if you have any further questions please don't hesitate to contact me,
Kindest,
Ben