Happy perhaps now is the time not to do everything - have a quick run round tidying up nothing major run Hoover over downstairs, bung some bleach down loo n shove dishes in dishwasher.
When they arrive say oh I just need to feed baby you know where the kettle is please help yourself and I will have x - leave some biscuits out, if it's lunchtime say there's some bread n some ham/cheese/salad please help yourself and can you make me x.
Or can you ask them to pick older one up from pre school environment route?
Ask them to watch baby or take baby for walk, sit in garden while weather is nice while you get an hr nap.
If you ask now by end week they should just offer or alternatively not come :)