I'm having a baby soon, my narcissist mother is insane and thinks she'll be caregiver numero uno but she is so, so incorrect

I've only posted on here once before, and it was kind of just a general background on why my parents both are terrible. This was my original post, but it's pretty long so I'll give the shortest TL;DR I can muster: https://www.reddit.com/r/raisedbynarcissists/comments/3xzxe1/can_i_post_an_introduction_tw_child_abuse_also/

Mother and father were long-time intravenous meth users. Father molested/raped me from an unknown age (possibly infancy!) until age 4. Mother relied on him for drugs, but my maternal grandmother got the ball rolling on their divorce and his loss of custody. Starting at age 8, my mother would invite him over to play board games. I didn't want him around for obvious reasons, but I had no say in the matter. Anytime my mother (physically/emotionally abusive) would get upset at me, she'd use what happened with my father to make me feel bad ("He knew what to do with you," "Why don't you go live with your father if you don't like my house"). She kept this up till I moved out at 18.

Okay so, fast-forward, I'm a miraculously not depressed or noticeably damaged survivor of abuse (I have solely my awesome grandmother to thank for my sanity). My husband, who I've known for twelve years, is awesome and supportive. We're having a baby, due in April. My mother is still involved in my life (going NC is way harder than I thought). She likes to tell me whenever my father texts her or shows up at her apartment unannounced (he doesn't show up often, but he knows where she lives). She's told him where I work and given him my phone number on a few occasions, and he's called/texted me and showed up at my job a few times (hasn't happened in about two years, and I've transferred locations since). I've told her about how it hurts and makes me very uncomfortable when she tells me about their interactions, and she always starts shrieking and telling me about how she was having such a nice day before I ruined it, et cetera. Seems like typical narcissistic stuff, I guess. Or just crazy person stuff in general? I don't know, really.

She's convinced that she'll be our baby's caregiver while my husband and I are at work (ha! hahaha!)... on top of the danger of my father potentially showing up at her house and encountering my baby (this is my worst nightmare), she's actually also permanently disabled and cannot lift a baby (two forever-damaged rotator cuffs), so she couldn't watch my daughter anyway.

I think I need some advice from you guys on how to let her down gently. She knows where I live, and moving is not an option right now. I don't think she'd try to hurt me (or could even if she tried), but I would absolutely not put it past her to attempt to snatch my baby or show up at my apartment and cause a scene in front of neighbors. For what it's worth, she doesn't know where I'll be delivering (I may even misdirect her and tell her I'm delivering elsewhere), and the only person who will know when I go into labor is my husband. I'll give the hospital staff a picture of her, and tell security to not let her near me. After this, I suspect we'll go no-contact... Do you guys think I've covered all my bases?

You're all a very supportive community, from what I've seen and experienced before. Any advice will be really appreciated, and I fully intend to pay it forward somehow. Many thanks.