I would say it is best to keep on plan, it is totally doable, I also did christmas and a week away, you just need to take your packs with you and get yourself in the right frame of mind.
Think it through in your mind, imagine yourself not eating food on the holiday, picture it, get it in your mind that you won't eat anything but packs, you can change your mindset.
I started LL on 1 Nov and was only 6 weeks in at Xmas, when I started I thought there is no way I can get through Christmas and a week away without eating, but by the time it came I had realised I could and did.
Imagine how good you will feel being so much slimmer on your holiday. You will still lose weight whilst away too, I lost 7lbs over Christmas, I have never before in my life done that. How good will that make you feel?
If you do decide to eat then lean protein with no sauces, uncooked veg is also best, so sticking with salads, but watch the dressing.
Booze is not a good idea, it can make you poorly on this diet.
It still needs to be burnt off, your body will use it as fuel before it burns fat. You won't stay in ketosis and you will start getting hungry. Then the ball starts rolling.
You are quite likely to find it very difficult to get back into it after the holiday, not impossible, but it will be harder than not breaking abstinence at all.
You can still have a fab holiday, I realised that for me it was about having a great time with my family, having fun, I did't need food or drink to do that. I think I learnt quite an important life lesson from that.
You should also bring this up in group, our LLC always had a group brainstorm in these situations and we all helped put forward ideas to help that person get through.