I was also at rock bottom after DS1 was born, and was subjected to an avalanche of criticism which certainly didn't help 
Just keep yourselves to yourselves. Get caller ID, so you don't have to answer when it's the PIL on the phone.
Reclaim your privacy. They will get the message in the end, especially if you reward them for good behaviour (i.e. if they visit at a mutually agreed time, and don't overstep boundaries) and ignore the bad.
It is hard to do when you're not used to it, especially if you like to be a people pleaser (like me
) but it will reap rewards 
DS3 is due in a few weeks, and I will be putting a lot of limits on visitors, and no one will be allowed to make remarks / criticism which I find unacceptable.
I am currently formulating stock answers to nasty remarks such as:
"Are you aware how rude and hurtful that remark was?"
or even
"I need to get on and and do stuff. Thanks for visiting tho"
Try to remember (I need to remember this too btw!) that if people are rude to you, you don't need to worry too much about hurting their feelings by asking them nicely to leave. You are not a bitch. They are rude and insensitive.
Good luck! 