Hi,
I'm sorry you're are having an extra stressful time having visitors and a new baby at the same time.
By the sounds of it the inlaws have been with you for a few months, I would have thought that that length of time with visitors would have you exhausted even without the a new baby.
There are a few things which make these type of situations difficult:
The inlaws are with you in your life for a very long time and it would be sad for this souring experience to taint your relationship for the next couple of decades.
Parents and inlaws can feel inherently more qualified on raising children and how things should be done based on their experiences 20 - 30+ years ago. You are experiencing raising a small child for the first time and will have some doubts and feel really confident about other things. They are probably commenting thinking that it will help you, even though you want to experiment yourself.
The inlaws are visitors/on holidays - you and your family and your helper are trying to live your everyday life. You still have the stresses of day to day living where as they can just focus on very little things and soley on the baby, which is/are grating at you.
You need to sit down with your husband, yourself and the in laws and discuss that you are feeling distressed about their feelings towards how the house is being run and how the baby is being looked after. Also to discuss what their plans are on going back home (tactfully).
If the inlaws want to do their own washing then they need to save up for a loads worth like anyone-else would. It's not a hotel service you are offering.
I felt encroached upon by my parents and inlaws advice when my daughter was born and started to feel animosity, then when my daughter was only 3 months old my husband was in a lifethreatening accident.
The inlaws and myself suddenly had to stop focussing on little things and think about a very serious situation. I realised how important they were in my life from then on and that all of the little things which seem like big things at the time don't matter. Your husband, you and the inlaws have a long way to journey together, try and solve this situation as peacefully as you can.