YTA but two things: 1. How sick was your niece? If it was the common cold I’m kinda on your mom/sister side. If it was a fever, your husbands. I take medicine every day for something I need it for but for other things I will attempt natural things. I think there’s a time & a place for both 2. How is your son? I grew up with a single mom & she’s been in a long term relationship since I was like 10. My moms family played such an important part in my life when I was growing up that if I had to skip Christmas with them because of her bf, I’d be upset. If your son wouldn’t care, then yeah stay home but I think if he is close to your family & used to these traditions it gets a little messier.