Have you thought about a toddler bed for #2 instead?
My two boys share a room and I was thinking about getting bunks but don't think I will now! We have DS1 (who is 5) in a single bed and DS2 (who is 2) in a toddler bed. I'm planning on keeping him in a toddler bed until he's about 5 as there isn't enough room for 2 singles in their room. We'll probably move house then anyway.