My kids are 2,3,4, and 12. I would rather I had twins or triplets. At least then they would be doing the same things at the same times!!LOL We made bedtime very simple after a lot of work
Basically, due to their ages and the fact that the little one's are afraid of the dark... The three younger one's sleep in the same room and the oldest has her own room. The oldest stays up half an hour after the little ones.
When my kids were stairstepped like yours we put them to bed at different times. The baby will not have the same schedule as your oldest. What I did was to put on Baby Einstein or something like it for my older one while I rocked and fed the baby. He would sleep in 2-3 hour spurts so I would take that window of time to rock and hold my daughter. I put them in the same room from the beginning so the baby would get used to the noises of her and she would get used to him... This is my 3 and 4 year old I am talking about... Didn't want you to think I put the 12 year old in front of Baby Einstein!!LOL
We also had nights of quiet time when the baby just wouldn't go down. I would hold both of them on my lap in the rocking chair and we would rock. I would also put the baby in the swing to rock. Luckily, a child that is almost 2 won't have a clear dominance over toys and such so they can just be considered "theirs" from the beginning with the exception of a few items. I would set the crib and all of that up now so your oldest gets to see now that he will be sharing. I would do a lot of talking about the baby to your son and let him help you with what he can for their room.
We really have never had a problem with it because as far back as they remember, it has always been the two of them. They don't remember the time alone to get jealous. Good luck and Congratulations!