Talk to me about kids sharing a room....

karelaorange

I've never posted on this board before, but thought some of you might have some insight.  We have a 3.5 yr old girl, a 9 month old girl, and just found out I'm pregnant.  We have 4 bedrooms, but want to keep one as a guest room because we have grandparents visit so often, and don't want that to stop anytime soon.

 We've talked before about the girls sharing a room, but now it will be necessary.  Who's done it?  What works?  My 3 yr old generally goes to bed at ~8 and is up between 6 and 7.  My 9 month old generally goes to bed about 6-7 and wakes up at 6 to eat.  I'm afraid having them in the same room means my 3 yr old will stay awake after that early feeding.  

 The logistics of this confuse me a lot.  Any advice you have would be appreciated.