I think it’s perfectly understanding that you don’t want to come out until after Christmas. And you should not feel obliged to.
You wouldn’t be coming out for them anyway, you’d be coming out for you.
You have to be in the right place. And you know what? It’s okay if that right place never comes at all.
I’m not saying don’t socially or medical transition. I’m saying you just don’t owe anybody in your family an explanation for why you do those things.
Though I hope you managed to find support from family members who are disposed to give it to you. That would be wonderful.