Here is my "plan"
I have a bassinet we plan on using in our room once he comes home. I will nurse him, change his diaper, and lay him back in the bassinet each night. I don't see the girls being a problem. Cooper sleeps like a rock at the foot of the bed. However, she also has no problem sleeping in her crate, which she does often. If things get too crowed or there is another problem, Cooper will be fine spending nights in her crate.
Maddie is the one I worry about adjusting to the baby the most. I want to keep things as normal as possible for her so she doesn't feel that we are "replacing" her with a baby. I fear changing her routine after 4 years would send her into a frenzy. I put her out of the bed one night I was not able to sleep comfortably with her curled around my legs, and she peed and pooped outside the door. I believe she has anxiety when it comes to change.