Having just talked about this family/holiday business with my therapist yesterday, I find this thread very relevant. Thanks for sharing it Jenocidal.
I would probably skip any family interaction this holiday and find a neat place to hang or some supportive (noncontroversial) friends to be with for the day. If a visit to grandmother is something you want to do, arrange it for after Christmas Day.
I, too, would be leary about accepting your aunt's invitation because, as Flower suggests, this could lead to the taking sides or divide and conquer mentality that exists in my family.
Though my mother lives nearest me, for years my siblings (who are spread throughout the U.S.) have vied and competed to have her at family gatherings being hosted in their home(s) during the holidays. Since one of my sisters won't speak to/interact with me, there is this unspoken but very ominipresent tension which I've danced around for nearly 5 years. This includes not being invited to gatherings where all other family members are present or having my mother feel uncomfortable in telling me of plans that don't involve me.
Even though I've tried to detach and let go of this dysfunction, it still impacts the relationship with my mother. I've decided this year, in light of the recent breakup with my fiance, that I will make my own plans independent of family. In other words, I won't build expectations (and subsequent resentments) by waiting or hoping to be invited. It's worked out that if my sister (the one who won't speak to me) is invited for an occasion, then I am automatically out of the picture. I am tired of this dynamic and am turning in my dance card (at least for this year's holiday season).
I feel sad but recognize that I can't change them or the situation. And right now, with all that I have on my plate emotionally, I just won't take on or sign up for any more chaos or conflict.
Thanks for letting me share my experience with this, Jenocidal, and for learning from all of you who deal with similiar situations.