sleeping arrangement of children

Hi. I have 2 children - 2 years old and 4 years old. Currently they are sleeping in seperate rooms.i have a helper. I'm also pregnant and due in april. But I am in a dilemma on the children and newborn sleeping arrangement. Need advise badly. I'm afraid that when 2 year old cries and wakes up for 1 night feed, will wake the other if they co sleep. Please advise. Thanks in advance mummies and daddies.