I have often read and admired the people (women) on Mumsnet who manage to prep most of it well in advance and only have to sit back and enjoy the days festivities. From reading those threads over the years we have improved our experience.
"Simple" is the hardest thing to achieve in my experience and only comes off when it has been very carefully planned.
Mother baby room - well stocked with nappies, wipes, a lidded bin, a comfy chair, soft easy access lighting by the bed, water and glass, cozy throw and as someone said up thread a little tree with fairy lights. Mum emptied out the top drawers for me and part of the wardrobe which was well stocked with hangers - very helpful to be able to unpack and shove the case under the bed. A dressing gown or bath robe.
Food - All of it can be done in advance as I learned here leaving only the turkey to be put in on the day! Delicious left overs the following days backed up by salads, soups, good breads and cheese. A rough outline of the weeks menu on the fridge door means anyone can put it together.
A commitment to sit down and not stress for large parts of the days and nights.
Everyone in my house has their own task for the whole duration - one in charge of rubbish and tidy up of sitting rooms, one in charge of loading and unloading the dishwasher, one in charge of setting and clearing the table over the whole duration. That works very well.
Oh! One final thing - we put a limit on amount spent on gifts and quantity. Saves so much time!
I am looking forward to reading this!