I also second big granny knickers!! They were a life saver to prevent any form of rubbing against my scar.
I had only packed for a normal delivery but had to have an emcs with DD. A friend of mine had said to take nighties regardless of how I deliver rather than PJ's. She said it'll be easier to just lift up a nightie rather than stripping PJ bottoms off, for any post delivery examinations. Not sure if you're UK or not, but I had ones like these https://www.matalan.co.uk/womens/sh...nighties/s2593388/half-placket-floral-nightie
They're not the greatest fashion statement but they were cheap, they served a purpose and I was still able to breast feed using the buttons.
We were in for 2 days and a couple of times Poppy came before my need to eat!! Annoyingly it was after DH left on the first night and I wished I had some snacks to keep me going. I'm also going to pack a couple of Robinsons Squash'd pods so that I can have squash rather than water all the time. Plus it takes up a lot less room in the bag than a small bottle of squash that I had last time round.
To come home in I wore my maternity jogging bottoms. They were soft, comfy and didn't rub. I also had easy to slip on shoes, but having SPD they were a must anyway!