Re: Prepping siblings
For the older kids, it was/is as easy as telling them we're having another baby. They all remember Levi being born and being a newborn at home, so they know what's going on and what to expect.
For Levi, we haven't really done anything. I don't think we ever really did with the kids when they were younger. IIRC we did try with DD, when pregnant with DS1, but then once he came and was here we realized it didn't really matter how much we did or said beforehand, it's all about the child him/herself and how s/he reacts and responds to the baby - some kids love it, some kids tolerate it, and some kids hate it. It's hard to tell how it'll be until it happens, kwim?
We have told him that there's a baby in my tummy. He pokes at my belly and rubs it, likes to feel Hiccup move around. But there's no way to really get him to connect that with an actual live newborn coming into our house!