We have had all four of our grandchildren from new born to stay over so have got it down to a fine art over 9 years.
We have a room with a cot which becomes a cot bed as they grow out of the cot. That's in one room ( which doubles as my craft room .
In the other we have bunk beds , and as we rarely have all 4 together that gives us plenty of space. Their rooms here have the same sort of things that they do at home , books , toys etc so for them its just a home extension.
The real difference is Nana's house, Nana's rules which both my daughters are happy with .
We do bath, drink, bathroom and teeth, story and bed for the littlest ones . Older ones can read in bed if they wish . We do have music in the little ones room.
The funny thing is , their parents often tell us how it takes an hour to get them settled and that they get up in the night etc. Not in our house they don't
We never change the routine , as they become potty trained they get up in the night and go to the bathroom , popping back into bed when they're done. Only a nightmare would see them materialising by my bed.
Now the 3 oldest are 9,6 and 4 we have the bunk beds on top of one another but until we were confident of ladder capabilities we had them down side by side.
We really cherish our time with them all so hope you enjoy your time too ( although I guarantee its exhausting