Hmmm, I hope this isn't true. I get you're upset that your son now wants to believe in 'farmer' christmas (too cute!!) because sister and your mother didn't respect your parenting choices, but killing christmas for innocent children to get back at another adult is really mean

I'd just do what N2L said Good ol' Farmer Xmas
I agree. Maybe you need to be sterner with your family in telling them you dont like it?