Day 43 - New Bed and a Question

When we bought this house one of the major disadvantages was there were only 3 bedrooms upstairs (two roughed in the basement of the addition) and the upstairs bedrooms are all very small.

We want the new baby to have his/her own room so put the boys together. As you can see from the before pics with two twin beds there was very little floor space left, and I couldn't use the dresser without moving Christopher's mattress. The solution was a bunkbed, or in this case a loft bed we put our own bed underneith. We splurged on a BelAir bed from The Children's Furniture Gallery. They are made in London, ON and only sold at the one store. We did save $300 by not purchasing the twin bed frame that comes with this loft and bought it at the Boxing Week sale. We love the stairs. I'm not confident in our boys climbing skills and I worried they would hurt themselves on a ladder.

I can't decide which size of mattress I want to put underneith. I'm thinking queen so that if someone does manage to fall off the bunk they will have a soft landing. Although the extra floor space the twin offers is nice. What do you think?