Oh! As Tracey has said cut them some slack. You've entered the BC world where reactions from family and friends are not always what we expect. You may have some drop off. I had a girlfriend who was over the top and didn't know much about BC but was quick to push me in her preferred direction which caused undue stress. She's no longer in my life.
As to your inlaw family it would appear that it is the normality of Christmas that your inlaw family are upset about.
As Tracey said try and be as normal loving and respectful.
Make sure you include them on your BC journey.
I'm sorry to read your story and hope for you that your treatment process is comfortable as can be.
Take care from Christine