Aimsmum,
I think you just sleep in what you are wearing - I wore a tracksuit in the evening so I would be comfy.
I am interested in the outcome of this - DS2 is a very bad sleeper and has had problems with ears galore.
DD will no doubt be given something to eat and I am sure they will keep an eye on her while you nip off for something to eat, if you dont want to do that, perhaps you partner could bring you something.
Best of luck