You are not expected to take over as teacher. We all have different ages kids and many have other siblings home too. It makes it virtually impossible to teach them if younger siblings don't understand.
Just leave the work. If you have a quiet period once it twice a week then that's great.
Quick ideas.
Draw some shapes for the 5 year old to colour in.
Letters for her to trace.
I've got mine a skipping rope.
Put both in the garden. Blanket on the floor. Books, blocks, drawing, snacks ... Anything.
Get your 5 year old to draw a picture of her family.
Draw a large square with sections. Ask her to draw food inside the lunchbox.
YouTube. Frozen yoga.
Draw a butterfly. Out different wiggly and swirly lines on the butterfly. Tell her to stay on the lines (pencil control)
Bath with bubbles and toys.
Put some coins under paper and let her use crayons to colour and make a coin print.
What has she done at school in the last 2 terms? Space? Get her to draw the sun. Earth. Stars etc.
Draw a bit rectangle and ask her to draw fish in the tank.
Get her to trace over numbers.
I've got a whiney two year old. He spends alot of time watching Bing. But he also loves vehicles and being outside too.
Put music on for both to dance about too.
Football in the garden. .
Daisy chains.
Mixing potions in water (mud, grass, petals)
Buy bird houses to paint from Amazon. Mine loved this.
Give them each a slice of bread to break up and go outside to feed the birds.
Let them amuse themselves in PJ's some days too.
Read bedtime stories.
Don't worry. If they do just ten minutes of something "educational" then you are helping keep their minds busy.
Some days have got to be about just playing and being lazy at home though.
Believe me that list is just loads of ideas. I've not even done half of them before. I'm just trying to think of ideas. But today in feeling very irritated and like I can't take 3 Months of this. My poor five year old is going to be bored next week I can tell. She is fed up after 3 days of nothing much.