My kids are a little further apart, like almost three years. But by then my evening routine with my first was so well-establiched, like you I really worried about how I was going to fit in a newborn to my marathon bedtime routine.
Kind of like the first child, you just have to start at the beginning and let a whole new routine evolve. It's just survival mode the first few months. I didn't really get a new routine down til about 6 or 7 months. because newborns and their needs change so much the first few months.
At first dad had to step in so we could keep the evening routine going for #1 as best possible. I would start now before the baby comes letting dad give the bath sometimes or read the stories or whatever. It becomes "divide and conquer" with two. And at first it happened to work out that the baby was in a sleep cycle during the first child's pre-bedtime activities.
I found giving two baths very tiring so a big turning point was when they could both be in the bath together (as soos as possible I combined the two bath times). This helped a lot.
Now the #2 is 18 months and we have a good routine going. They take their bath together, put on jammies, brush teeth. Then the older one quietly plays in the room with us while the baby gets to read books and cuddle with me in the rocking chair. Then she goes in bed, and the older one gets her mommy time with books and cuddling on her bed. The toddler sometimes falls right asleep or just rolls around in her crib listenening. It works out fine.
You'll work it out! It won't fall into place right away, just be prepared for a few months of upheaval and things going by in a blur. I found the transition from 1 kid to 2 even harder than just having the first. It's hard to start splitting your attention between two. But then I realized, ok they are BOTH getting less attention from ME, but now they have each other to give/get attention from. It works out. As soon as you witness your first tender moment between the siblings, you'll know your family is multiplying in love, not dividing :)