Any chance you could keep the baby in your room a little longer? I am concerned about sharing with a 2 year old especially given his sleeping patterns. When I was a baby my 2 year old brother used to throw toys and pillows in my crib while I was sleeping. Fortunately I didn't suffocate but my mom had many scares digging me out of the crib. It's normal for a young 2 year old to do things like that. If your 2 year old is closer to 3 he shouldn't be doing things like that anymore (or for much longer).
To answer your question about how to get them to sleep in the same room:
1) You could just put them both in there at 7:30 and let them work it out. Chances are your 2 year old will keep your baby up and then she will have bad sleep habits too.
2) You could help him develop better sleep habits by using some sort of reward system. I'm thinking like a sticker chart or something simple like that. Get him to the point where he goes to sleep quietly and quickly before moving your baby in there. If it sticker chart doesn't work just start putting him to bed earlier so that he's asleep by the time the baby goes to bed. My daughter went to bed at 7:30 until she was 10 years old and then she earned an 8:00 bedtime by going to sleep well and waking up with a good attitude.
I don't blame your 11 year old for wanting his own space. It would be better for the baby to have her own space but not at the expense of your 11 year old having to share with such a young child. He needs his own space, especially at this sensitive time when his body is changing.
I'm in a little bit of the same boat with a baby boy on the way and a 10 year old girl. The baby will room with me for awhile until we can figure something else out (like moving or converting the loft into another bedroom).
I hope all goes well!