help me re-arrange our sleeping space?

[wombatclay]

We're a family of five, with number 6 on the way and I'm running out of ideas for where everyone can sleep!

We live in a small 2 room cabin and sleep in the upstairs "sleep loft".  Imagine a triangle of space under the roof and you've got it!  Right now DH, 18mo ds, and I share a queen sized bed (an IKEA low frame, so the top of the mattress is maybe 2 feet above the floor?  A full height bedframe doesn't fit into the vertical space available.).  Dd1 and dd2 (5yo and 3yo) each have a twin sized air mattress that goes on the floor by the "big bed" but most nights dd2 climbs in with us at some point.

The problems are:

--all the kids (inner and outer) are growing and there just isn't room for everyone on the "big bed"!  DD1 would like to be on the big bed too some nights and there is literally no space for her, I get shoved onto a sliver of bed, and ds can't/wont sleep unless he can lay flat on his back so when dd2 climbs into the bed that's more or less the end... ds thrashes about till morning, keeping me awake too.

--DH has dust mite allergies and while we have tried the mattress on the floor solution in other homes, in this particular house that causes serious problems (month long sinus infections for example).  He is on medication, but we're caught between a low ceiling and not being right on the floor.

--where the heck to put the new babe come September!?  When ds was born DH took dd1 and dd2 and slept with them on a queen sized air mattress.  It was hard on his allergies but gave ds and I space to babymoon.  Once dh returned to the big bed the girls shared the queen sized air mattress happily for a few months (then there was all out turf wars resulting in two twin sized mattresses).

So, given the limited space and the expanding population... any ideas about where to put people?  A king sized bed with a twin bed "docked" to one side and a bassinet on the other would be ideal, but till we win the lottery that probably wont happen.  And it probably wouldn't fit anyway.  LOL

[To-Fu]

Hmm, what about sleeping sideways on the bed?  I've heard this work for some other families... your feet may or may not hang off if you're all stretched out, but it gives you way more horizontal space. 

Let us know what you decide!