I'm sorry this is going so rough. It took alot of courage to step forward and be yourself to those you love. Being met with rejection must be so painful.
They're probably concerned as parents, in-laws, and grandparents more than anything. And their reactions are probably more immediately emotional than logical. Give them some time. Let it sink in. Keep showing them you are still you and let them know you are all happiest this way. Hopefully, they will come around.
*hugs* to you and your family-both blood and chosen. Let us know how things are working out when you're up to it.
I'd rather be hated for who I am than loved for who I am not.