How do I have the conversation?

Long one, buckle up… Currently 29+6, both my mum and MIL have offered to help with childcare when it comes time for me to go back to work next year. So far the rough plan is for us to put LO in nursery 3 days a week & my mum and MIL each have them 1 day a week. I work shifts so we’ll need a little flexibility around this. Recently I’ve started feeling more uneasy about MIL taking care of our LO for several reasons: 1. Things didn’t go well when she looked after BIL (husband’s bro) & SIL’s first child, to the extent that they stopped their childcare arrangement with her altogether and instead put him in nursery an extra day per week (and declined help with childcare for their second child). She constantly undermines them both to their faces and behind their backs e.g. mocking them for sticking to a routine and secretly giving their LB ice cream even after he had an established CMPA. SIL told me she once came home from work and MIL had rearranged her whole kitchen - I’d flip 😅 2. During the time she looked after their LO, MIL would complain about having to make the 40min journey to theirs; we live a 45 min drive away, probably longer with traffic. 3. She has made some concerning comments such as “kids didn’t used to have allergies”. 4. She has a rotten temper. Last time we went out for dinner she lost it at FIL because he hadn’t heard her properly (his hearing has been worsening recently, something we’re all aware of), raising her voice so much so that other tables looked over to see what the commotion was. 5. She can be cruel to both her sons. She constantly body shames my husband about his weight (honestly I’m going to call her out next time, I hate it sm), and was super nasty to BIL for only coming with her older grandson to her birthday lunch - SIL was 4 weeks pp with their younger child at the time and had made clear from the start that she wouldn’t be able to make it. MIL said, “Could she not just make up a bottle?” and also complained that she didn’t receive a birthday card from BIL & SIL in addition to the handmade one from her grandsons. 6. OH often says she “ruled with an iron fist” when they were growing up. Both he and BIL were scared of her. I myself grew up with a stepmother who was aggressive and abusive, and I feel strongly that I don’t want my child exposed to that kind of toxic energy. I know that people are different grandparents than they are as parents, but I don’t feel like I can trust her unsupervised, especially when she struggles with her temper and will undermine requests regarding the kids’ care when she can. 7. I’ve seen how bossy and micromanagey she is re. parenting with BIL/SIL and also my husband’s stepbrother and his wife, which makes me want to keep her at arm’s length or even nip it in the bud at the start when LO’s born. Initially I wanted to approach this as a clean slate (“we’re not BIL/SIL, hopefully she’s learned from that experience” etc). But as a recovering people pleaser I’m determined to advocate for my child in a way that my dad did not for me (side note: we will visit him but he will never be responsible for my child unsupervised). I know we ultimately need to set boundaries, but what I’m seeking advice on is how to have this conversation with my husband first. I can tell that he’s really excited to be able to give his mum another grandchild since things didn’t go well with her first two (she was really upset when BIL & SIL stopped her regular childcare slot, and is always complaining that she doesn’t see enough of her grandsons). I’ve already warned him not to over promise as this is all still quite far in the future. But he’s already saying things like, “I think it would be nice if she had a consistent 1 day a week of looking after her grandchild”, which I’m resistant to because of A) my working irregular shifts - what if her day falls on my only day off that week? B) it would mean engaging with her more than I can handle, and C) as the birth draws closer I’ve been feeling increasingly uneasy about the idea of her having our child unsupervised. I really want OH and I to approach this united, however we handle it, and I’m scared that it could negatively affect our relationship if we don’t. Over the past year he’s been working REALLY hard at saying “no”, standing up for himself and having my back, but setting & holding boundaries etc is still very new to him after almost 40 years and he still has a lot of anxiety due to how he was raised. Also want to add that he’s been an absolutely dream during my pregnancy, looking after me and taking over household stuff when I’m not feeling myself. Hit me with your best advice mamas 🫶🏻