I know, i had to take another look I thought surely I haven’t just seen 2 kids in that. I’m not usually one to stick my nose in but I do hope they got there collars felt.
I would say pull the curtains at least partially, I had a nice little snooze while on the very few double manned runs I have done.
I don’t think you can see much going on in the cab anyway, even in daylight, unless you are very close, so even with the curtain open it’s doubtful anyone would see another person there. A hi viz draped over the passenger seat tends to look like a passenger to me.
JLS Driver SOS:
To be honest, if I was the sleeper, I wouldn’t opt for the top bunk, could be pretty scary in an emergency brake
In the USA where double manned or team trucks are often used, the driver who is in the sleeper must be in the lower bunk by law and have the net set up (although I have never seen or heard of it being used) 
I double man and the bottom bunk is constantly in use… Its a perk of the job and has been for the last 8 years 