Making Room for #3

I am quickly approaching my 34th week of pregnancy, which leaves me a short 6 weeks until my due date (but neither of my other babies ever lasted that long in the oven).  The closer I get, the more I realize how little I've done so far to prepare for my little girl's arrival.  My two boys (4 and almost 2), will be moving into a room together so that the nursery can be used for the new baby.  So the biggest issue is... well hold on, there's a few issues here:

1. My little guy has been using the crib up until last week, where he finally refused to stay put and would climb out every time I put him down for bed.  So we removed the railing and now gate the doorway so he can't wander out of his room at night.

2.  We are moving the little guy into his big brother's room once the baby arrives, but this room barely has room for a second bed.  If we do get another twin, they will have no room to play in there.  Bunk beds are too dangerous for the little guy, who would probably try diving off the top, toddler beds would be a waste of money because they will grow out of them in no time, which leaves me with what choices really? Hmmm? I need help!

We just moved into this house a little over two years ago and are already growing out of it. Has anyone else had this dilemma, and would you mind sharing with me how you overcame it? I'm just quickly running out of time and ideas. We have a spare "bedroom" in the basement, but it's become my husband's office room and I don't think I would feel comfortable having any of my kids down there alone quite yet.  Ohhh decisions, decisions.  I'm sure I'll figure something out (I better).  But any help or advice would be greatly appreciated.