Hi D.,
Our two boys (4 and 2) share a room for exactly the same reasons you mentioned. We moved the baby's crib into the older son's room when he was about one year old and had been sleeping through the night consistently for some months.
We have a few small issues: like the baby still has to nap in the pack-and-play in a separate room during the day, or they keep each other up, and it was work to get them both to sleep at night in the summer (still light in their room with the curtains closed until almost 8:30 at night: haha!).
But we just take it as it comes, and we've gotten all the rewards of having two boys who just love being together, and are *learning* to share!
Good luck!
t