Not going to buy into all the other stuff.
Op you clearly care about the wellbeing of your entire family, your DSD included.
It sounds to me that you're experiencing anxiety in the lead up to new Bub arriving and wanting to sort as many situations out as possible beforehand.
I think most of us can probably relate to that!
I think it's commendable that you're coming and asking advice. It shows you care.
I also think though that to avoid further stress to you, your Bub, your DD and your DSD, you need to push back on DH and his ex.
Uniform issue - DH can do it
Lunches - DH can do it
Drive to school - DH can do it and be can get off his effing phone while he is.
Yes this is about DSD and her dad having time together, but he needs to actually contribute meaningfully.
Your whole family will need time to adjust when Bub arrives and your DH needs to step up. For ALL his kids and his wife.
You do not have to sort any of this. You just need to love your family and if DSD's parents aren't phased by any of this, take that as a sign that you don't need to worry and push back on them so when DSD is at home with you guys you can enjoy your time together.
I wish you all the very best for the rest of your pregnancy xx