Shower advice needed

I'm trying to get my baby shower guest list in order and I've got a small problem. There's two people I REALLY don't want to invite, but I'm worried that by avoiding drama I'll end up creating more drama. Here's the deal. The first person I want to avoid is my mother in law. Long story short, she and I haven't spoken in about two months, since I asked her to take my ultrasound pic off her facebook, and to stop referring to the baby as her grandson, since we're waiting to find out the sex. She obliged, but only after an completely incoherent rant claiming my requests for subtlety and privacy weren't "normal." I wound up telling her to bugger off, and blocked her number because she was stressing me out so much. The other person is my aunt's wife. She and I got into it last Christmas when she kept being condescending and trying to start a fight with me for absolutely no reason. At one point after dinner, I was petting my dog when she came from ACROSS THE ROOM TO wipe down a wine bottle I'd just handled after touching the dog before scolding me like a child. I firmly told her not to speak to me that way, but she didn't give a f*&@. Later that night I wound up going off on her for what turned out to be my dog's mistake. When I apologized the next day, she suggested I leave my dog at home whenever we come by. We live out of state, and never had an issue bringing him before. I told her I wouldn't be back to their house and left it at that. Then when we had to put him down in March, she sent me a text offering her condolences like nothing happened. I didn't respond. Right now, I feel like it's more important to fix things with my MIL than my aunt's wife, who I've never really liked. Plus, my aunt's wife had a habit of taking over at other people's parties, which she did 5 years ago at my sister's baby shower. The bottom line is that I don't want a scene in front of my friends, many of whom have never met any of my family besides my mom. And I don't want to spend the day in a bad mood because people are being disrespectful. Should I risk making things worse by keeping them away? If I don't invite my aunt's wife, I have to be very clear that she isn't invited, which might upset my aunt. She's already mad she couldn't buy me a stroller that I didn't want, and like the other two has a problem maintaining boundaries. I want my aunt there, but if she brings her wife I'm gonna ask them both to leave. Is that unfair? I planned to send my aunt's invitation to her office and include a note saying her wife isn't invited. If anyone has a better suggestion, I'd love to hear it. I'm not a very confrontational person, and just thinking about this has been stressing me out for months. Sorry for the long post. (Update) I spoke with my cousin who confirmed his stepmother's dislike for me, and suggested I just tell my aunt not to bring her. He claims she won't care, so I'm going to trust him on that one. Still no decision on my MIL. But thanks for the help!