I spoke to my step-MIL today (I called to thank her for sending a gift to our family). She invited us to go to see her and my FIL (and my wife's step-bro & his wife) for TG (they live about 200 miles away).
Here is my thought... What if I act "as-if?" Act as-if we were going. Pack some clothes for the kids, get the car ready, etc. And if she says we are not going to visit, then I just tell her we are going anyway, throw the kids in the car, and drive off without her... tell me why this would be a bad idea. Somebody talk me out of this...
For the record, the family on "my side" has nothing planned.
I don't see any downside to this. It may alienate her, but if she is alienated, it is of her own doing. It's her family, but...