Hey Ally
As long as it turns a colour, you are in ketosis, if it is very dark it can indicate dehydration, so make sure you are drinking plenty.
I am sure your family will be fine by xmas, why would you want to take a week off so you can put all that weight on? Almost everyone will gain weight over xmas, exept you, and that is a real buzz, I lost 7lbs over the xmas/new year fortnight last time.
I found it relatively easy once they understood that I wasn't wavering, especially becuase someone else wanted me to!
It makes no difference to them whether you eat or not. It isn't going to ruin their holiday or yours. I found I enjoyed it just the same to be honest, it was the people I was sharing the holiday with not the food.
I am pretty confident again this year that I will be totally fine.
Hope you are having a good.