Don't blame yourself for inviting them over, you even paid for the ticket!
Without wanting to sound all doom and gloom, it's very likely that it will be a hard few weeks, with a screaming baby and permanent hanging out boobs. You will be tired, emotional and bleeding and need yor privacy.
So, get dh to book them a hotel or b&b for at least a week. Then if they come to yours, they take the sofa bed and you get the bedroom, that should include a tv, books, maybe a kettle.
You will need privacy and a place for daytime naps, do you honestly think you can do that in a living room?
If your DS wakes up from the baby's crying then your DH should go to him and let you deal with the baby. Besides, in a two bed house I imagine you will hear the baby from every room!
If all else fails, and your DH insists he wants his parents around and in the bedroom, then you pack a bag and go to a b&b yourself. Honestly, it will be less stressful and you'll get a lovely fried breakfast every single yummy day! 