Who should share a room?

Hi Guys! Just looking for some thoughts on my situation. We live in a 3 bedroom home (no option to move right now as we are in a 12 month contract) I have a 5 year old girl, a 2.5 year old boy and a 2 month old boy.

My 2 month old has started to get too big for his bassinet so will be needing to go into his cot soon. My daughters starting school soon and has a different bedtime to the other two and has had her own room since she was born so I’m not sure how sharing would go.

My 2 year old son is a typical two year old and has tantrums etc so it makes me uneasy how sharing could go, he usually sleeps all night but wakes early and worries me he could try “help” his brother get up or something. My bedrooms way too small and can’t fit a crib in so that’s not an option. Thanks I’m advance :)