Kids sharing a room

For those of you with multiple kids. Do you have them share rooms?
We own a 4 bedroom. This will be #4. 
So you can see my dilemma. Houses are not selling well here and that means we are stuck for a while. 
I have a 7 year old girl
6 year old boy
3 year old girl
I know my 7 year old will not want to share her room. My son wouldn't mind. I'm not sure if the youngest should. Since babies wake up all night. We will room share and co sleep for a while. But I will have to make room arrangements soon. So that they can get used to the change slowly. 
I'm just not sure how to do it.