I think you can structure a bit of the time, for example you can make sure the kids all have a go at that day's art/baking/music project or whatever, and obviously you need to structure meal and nap times, as well as toilet times, or it would be complete mayhem. Then you can structure on the basis of whether they are learning inside or outside, whether they are in mixed age groups or in separate rooms, and so on. In addition you need to make sure at some point that they all have the basic skills for school, which are very simple IMO and include:
How to hold a book and navigate pictures and a few letters/simple words (quite different from 'reading' of 'phonics').
How to turn on a computer/iPad and use very basic software.
How to deal with being thwarted by other children without completely losing it.
How to take turns and line up patiently.
How to address teacher type people.
How to get coats and shoes on and off.
How to sort, count and order things (pre-maths).
How to hold a crayon or fat pencil so you get a good result.
How to paint without flinging paint everywhere.
How to help clear up.
How to ask for help if you wet your pants.
How to eat your lunch without making a fuss.
How to get out if there is a fire alarm without panicking.
How to concentrate on one thing for about 10-15 minutes without running off.
How to recognise your name on a peg or drawer (bonus points for being able to sign it in a card).
Now if every child in the land managed all this, I am sure Reception teachers would feel they were well served. I am of the mindset that this is just about all you can usefully teach them, as the rest is very dependent on whether they are ready to learn it. You can offer instruction in other things to kids who are bored or asking to do things, but it is completely immaterial whether they 'succeed' as nearly all the time they will crack it by age 6 or 7 anyway.
Weighing babies does not make them grow. ;.)