That last point just helps your eldest to realise that baby has to wait for attention too, the same as when they have to wait
Before I had an obvious bump, my daughter struggled to understand it as much. Now I have a bump, we talk about it a bit every week. I just try to include her as much as possible. If I’m getting kicked, I talk to her about it. If she wants to read me a book, I ask if the baby can listen too. When we watch shows or read books, we talk about others having siblings and how she will soon. If I do any shopping for baby, I include her and let her make decisions on what she thinks the baby will like to wear etc. When the baby is here, I’m going to try and give my daughter 1 on 1 time often. And I’m going to let her pick certain teddies or toys that she doesn’t have to share with baby so she doesn’t feel like everything has been taken off her to share
Once I started showing, we just kept talking about the baby in my tummy and that he was coming to live with us and that she was going to be a big sister. We found out what we were having so we could be very clear with our little girl that she was getting a baby brother. But obviously if it’s a surprise, you don’t need to do that. But I would just keep it to ‘baby’ rather than saying ‘brother or sister’ all the time, as can be confusing. Lots of ‘practice’ on a baby doll, showing to be gentle and careful. Lots of reassurance that mummy and daddy will still love them and you’re looking forward to their help with the baby. Once baby is here, involve them in as much as possible. One-on-one time as much as you can. They’ll probably start acting like a baby for a while, fully indulge them as it’s really normal. Lots of praise. Make the baby “wait” while you’re helping your eldest. Baby will have no clue but just say out loud “I can’t pick you up right now, so and so needs my help”.