I am so sorry about your sister.
I have read through most of the responses and I am touched by all the compassionate & caring replies. And everyone's opinions are their own based on thier own life experience. So, I humbly give you mine.
Do what you want for yourself.
You are hurting, you are sad, you don't "feel" the celebration & thankfulness right now in the season. That is ok. You don't have to feel it. It IS okay for you to listen to yourself and do what you want (and it is not selfish, it is survival). Why do I say this? From my experience.
My mom died 4 yrs ago September. Tears still come to my eyes thinking about it. My birthday is in October, my DD's & husband's and my 2 sister's in November, and then Thanksgiving and Christmas which my family celebrates. So many of my family told me to "do it for mom" or "would mother want you to miss this" or "we have to keep plugging along" and you know what happened? I resented it! If I did "celebrate" and plod on through; I was angry and resentful. I felt ignored. One time I was completely ignored by my brother & SIL when I said I did not want to celebrate my birthday and they told me to meet at a bar to discuss handling mom's ashes and "suprised me" with a celebration - that did not include my husband and 2 children. I was furious!
After this dismissiveness, I decided to start doing what I wanted. And you know what? I was able to find some pleasure in holidays while achingly remembering/ missing my mom. Listen to your needs...
I like the idea to have a family meeting or talk and let everyone feel free to say what they want/ need in the upcoming holiday craziness. And then be honest about what you need/ want and are willing to do.
I have ended some family obligations after the death of my mom, all the while creating new traditions...my thanksgiving went from over 50 cousins to a small (6-7) dinner away in the mountains where my mom took me every year for my entire life, and I don't miss anything about the change we made.
Listen to everyone but in the end take care of your needs.
My heartfelt condolences,