What about adding a cot (with the side taken off) as a sidecar to your bed? That way there is more room for everyone, yet everyone is still within arms reach?
I just can't imagine fitting 4 in our Queen bed... its squishy enough with the 3 of us! Although Kel I agree with the doona trick... we have a King doona for our Queen bed... after much insisting from me cause I spent the first half of winter freezing (thanks to the 2 male doona hogs LOL)