Hardest parts would be getting a baby sitter, my kids have "special requirements" so tend to get two babysitters and split the kids up on the rare occasion we go out.
My husband works away a lot so when the toddler has been sick through the night the cosleeping baby hasn't been keen and there is still school/nursery runs always needing done regardless of the baby has slept well or not.
You've don't it twice before so the baby stage will be a doddle, you really just need to be prepared with stuff for your other kids.
Routines help me so not just the breakfast by 9, lunch at 11:30, snack after school and dinner at 6 and everyone ready for bed 7:30/8
But also when I'm about to feed ds3, DS2 has playdoh, pens, I pad or something that he enjoys. Cartoons for ds3, he's tube fed and I need him distracted. Ds1 keeps himself entertained.
Cooking (I don't know how hygienic this is) but while the kids are eating snacks at half three I set out all my ingredients, marinate, chop so when I come to cook when DH has finished work it's so quick and easy. Or slow cook in the mornings.
Looking clothes out the night before, meal planning and online food shopping always seemed like things ultra prepared people did unnecessarily to me but actual lifesavers now. As are slings (Hana for a tiny one and Tula for when they are bigger) reigns for the toddler and fresh air every day.