Lisa - We are in a four bedroom house, with 4 kids. Our 8 and 3 year olds currently share, and our 10 and 7 year old currently share. I have an office as well. We have JUST reached the point where things are getting uncomfortable and our 3 year old is driving our 8 year old bonkers by leaving his laundry all over
. So ... I am loosing my office. 10 year old is "getting" his own room (the office) because he is the oldest, and 3 year old is moving in with 7 year old (leaving 8 year old with his own room by default).
They have always loved sharing a room, and for a couple of years we had the oldest three in the same room because noone wanted to be alone. So ... all that is a rambling way to say that yes, I think sharing is great and the kids love it and its fine. You might want to NOT have them share until baby is sleeping through the night ... but I always had my babies in my room until then anyways.
And ... my oldest two are 15 months apart (full bio sibs), our bio son is 18 months younger than #2, and then #4 arrived three and a years later. BY FAR ... its been easier in the long run to have 3 close in age. They play so well together and are on the same ability level which makes it easier to do family things together (ie biking, hiking etc).
Our "baby" has been more work (in a different way) because of the big gap in age.
Jen