Michelle if its mean for you to say No to your IL's about this then I must be mean. I had the inlaws stay with us in our 2 bedroom flate for a little over 2 weeks when Evanwas born. They arrived a few days before his birth. They did not come to "Help" they came to visit & meet the new grandchild. By the time they left I had been so nasty to them, it changed my relationship with them forever. Oddly in a good way. they learnt how to deal with me & I learnt how to make them realise to back off. FIL wasn't so bad, he stayed out of my way & let me get on with things but MIL was just a fuss pot. Wanting to pick DS up the moment he stirred etc. Wanting me to wrap him her way, feed him her way, sleep her way etc etc. She was pushy pushy abouthtese things but she wouldn't shut up about her idea's & how she did it with her kids. I think I really suffered from the baby blues alot longer then normal because of them staying with us in that time after the birth.
When #2 was growing I asked DH to tell them that while I amhappy for them to come down for the birth they will need to find alterative accomidation after the birth. DH said I was just being nasty & to get over it etc. I have a history of being difficult with his parents (long story but IMO they only get what they dished out)so DH seen this as another way of me being "Difficult" just to be nasty to "his" parents. He eventully did see my side & the point I was trying to make. But I emailed his parents explaining that I did not want them to stay with us after birth as it was just too much stress for me last time. They never actually said anything about the email but did leave it till DS#2 was about 3 -4 months before they came down. It was so much easier on us. DH probably wouldn't admit it but I was right to put my foot down & say NO you can not come this time.

Anyway my point is, its ok to say NO you have your DH's support on this as well. Don't get him to tell them & don't wait for them to offer the help. Just email them now & say you are greatful for any help she is wanting to offer but this time round you would like to be able to spend the first few weeks (even months) with your new baby with out the extra "Help".