i dont see what you are asking is too much but some nannies are pickier than others (me for example) i NEVER iron!!!
nannies generally do nursery duties, ie was the childrens clothes, change beds, tidy up toys etc - but some dont have any (like me, but only as mb and cleaner do it)
i wouldnt object to chopping a few veg,putting food in oven - but no complaining about my cooking
if your children are too tired to eat at that time, i would get the nanny to make tea for the children and give it to them about 4.30/5
if she is nice she may make a big shepherds pie and you can have some, or you might have to come home and cook your own tea, just as the nanny will have to do once she is at her home
i know what you mean about sleeping, my 3.6 and 9mth both sleep 2hrs every afternoon
most nannies are flexible and i have picked up dry cleaning, taken dog to vet, taken shoes to be reheeled, picked up parcels from post office etc
you do need to pay your nanny when children are at nursery, as the nanny is on call, incase they are ill/fall over etc - tbh i dont think you will find one who will work 7-9 and then come back happily at 12
as long as you are honest at the beginning then shouldnt be a problem