I would say its time to learn the kitten shuffle!

If you can get a bigish bed for them to sleep in great - but its probably time they joined in with family. I bring my kittens downstairs out of the maternity suite sometime between 4-6weeks old. If they are mobile enough to be jumping out of the box its time they joined in , try and keep them confined to one room if you can, and place a couple of litter trays in there so mum can start to teach them. I start weaning at 4 weeks too so it wont be long before mum stops cleaning up after them!

You just need to learn to shuffle and double check every time you open a cupboard, close a door etc!