Sleeping arrangements (sorry, a bit long)

I've decided to post it here, but really the issue applies to newbors and older kids as well.
My 9 y.o. and my almost 4 y.o. share the room (it used to be the oldest son's room, then the younger one joined him at 18 months). MY youngest son has a room to himself. I am due G-d willing in Jan/Feb, and we were thinking of putting the three of them together (space permits that with bunk bed) and give the baby the other (little) room after the baby turns about 8 weeks. Now, the 2 and 4 y.o. both go to bed at the same time (bedtime routine is together, but sleep in separate room). Older one goes to bed after 8.
I am getting worried because my preschooler has a tendency to wake up early pretty often and get very loud (turning on lights, jumping on his brother, waking him up - which makes the older one tired for the rest of the day, etc). We have an alarm clock set up, but he seems to listen to it one day and ignore for the next three, running up and down the hall waking everyone up and getting loudly upset if he doesn't get attention right away. We talk (he is very bright and verbal) to him, explain, offer praise for good nights, etc, but nothing seem to stick. I am terrified of what happens when the baby comes and I am up all night nursing. Besides, now I am having second thoughts about putting all three together because I dont want to disrupt the sleep for all three.
My oldest told me today that he is fed up with the middle one waking him up and wants a room of his own (the only option now would be to join middle and young ones together and give the little bedroom to my bochur which means he would have to share it with the baby soon - not that practical either).

So, I am stuck.

any advice from experienced moms is appreciated.
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Moderator Joined: Dec 18 2008 Posts: 3612

Would the 2- and 4-year-olds go to sleep nicely at the same time in the same room?
Why is it not practical for the oldest to share a room with the baby?