I'm so sorry it all went so badly with your mum. However, I would listen to what she's saying here -- it was a shock to her system, which is the case with a lot of people who are homophobic on the general level but possibly not on the personal one, once they get used to it. The fact that she's given you money for the car certainly is passive aggressive, but if she's anything like my mother, it might be her way of starting to apologise? She may come round.
If she doesn't -- well, she's wrong, your kids are fine and your husband understands and you've done nothing wrong. But I would take this kind of gesture as hopeful.
My mother is extremely homophobic and when she found out I was bi (actually she thought I was a lesbian) she absolutely hit the roof. She said she never wanted to hear anything about it, etc etc. I ended up marrying a man, but he has an intersex condition (before anyone says anything, this is how he likes it to be described) which means he's infertile. I had to explain this when we went for IVF, having always known IVF was the only option, and she once again went mental, demanded to know if I meant he was "a tranny" (i.e. a trans man; he's not) and why I couldn't've Married Someone Normal etc. Obviously I was furious, cut her off, but she apologised and is now very fond of him. I think people like these women, who are knee-jerk bigots, react terribly and cruelly to the shock of knowing People Like That might be in their lives and close to them, but they can claw it back. I'm generally okay with my mother now.