Wow, this sounds like it's going to be quite the heavy, emotional trip for you. Good for you for thinking ahead of how best to handle it.
What is the bare minimum time you have to be there? What are some valid excuses if you have to leave early? Why can't you just say you're feeling under the weather this weekend and regretfully decline? Choose your battles. Will the benefit of going to this family get-together really outweigh the strain put on your emotional psyche?
dolce, the further I got in recovery as an ACOA the less I could physically stand to be around my family, particularly my AF. The intensity of this feeling was too much to communicate to anyone at the time. There was no point in trying to raise the issue any further because I was not in a place to deal with it comprehensively anyway. I just had to get out. Staying close was not helping me or my family anymore anyway.
End point: this "sacrifice" of your time and emotional well being probably isn't going to change the dysfunction for better or worse anyway. Let go of the guilt for not being okay. You ARE not okay right now, and that needs attention.
Though not necessarily the attention you're going to get if you *explode* (so to speak) on your family. Either through journalling, more posting, or counselling. Right now you need new life skills that you're not going to find at home. Your ACOA life skills have finally become too obselete for you to use anymore. Are you doing anything else in addition to posting here to deal with the growing pains of recovery?
FWIW, you are going to look back and realize you deserve an emmy for all the strained holidays you've survived by performing through.