Damn I'm sorry. The only thing I can suggest is to give her space, as much as you can. You don't deserve this.
If you have any kind of support system outside of her, now is the time. I would stay off Facebook. Trying to do damage control there with a conservative family is probably going to do more harm than good.
It's going to hurt more before it gets better, but with time and some effort, it can get better. Care for the kids as best you can. Then care for yourself as best you can. Then care for your wife.
You have every chance of being a pretty woman. It make take hormones and time and hair removal, and maybe some makeup magic, but there will probably come a day when you can be proud of what you see in the mirror.
Regardless, who you see in the mirror is more important. Do your best, and the rest will fall as it may.
Your mother is saying nonsense. My mom knew I liked girls when I was 4. She thought that was normal, because I'm a trans woman, but it was obvious even then.
I'm sorry. You don't deserve invalidation. You deserve affirmation. You don't owe your mother anything, but it's possible that your dad or a grandparent can be an ally for you with the rest of the family.
How can you tell them? I don't know. "Hey, I have something important to tell you." Will probably force the issue.
You don't have to come out, but if you want to, that's how I would start.