Terribull - the CD player is a good idea. We usually have a pleasant day when our two little ones are doing an overnighter but come bed time it all turns into a nightmare. I put it down to them not being used to our bath, story, bed routine. I'll try the CD. I've found that having the radio playing quietly on Radio 4 (yes!) whilst the DGD are doing art or craft work at the table helps their concentration and even promotes a little education, as in 'Grandma, who's Boris?'
Regarding bunk beds, my son fell from the top bunk when he was seven and broke his arm, so I'd be wary of them for little ones.