I'd let your husband do his thing but work with the nurses too; make sure you are showering or elsewhere when they come to visit so there's nothing to "see" in your and the baby's room, etc. Just give your husband simple instructions; at your house, if you have visitors from his family, you're "not receiving". For quite awhile it should work okay because the baby will be so young and not going out much. Get a schedule going with the baby so s/he is at activities when out that are not in his family's normal orbit, don't tell then who sits/cares for the baby or when you won't be there, etc.

Try not to argue/fight with your husband, just keep saying what you want. No one can argue with what you want because it is what you want. Does not matter what they think of what you want, it's what you want. You do not have to convince them of anything or give reasons or excuses or anything -- you are allowed to want what you want whether it is right, wrong, crazy, a good idea, a bad idea, whatever. Your sureness and calmness in discussion will probably go a long way to reassure your husband and remind him how simple it all is. You don't want to have anything to do with his family. Let them think you are a ^itch or unreasonable or that they're wonderful people; you don't care because they're not part of your world. Don't worry what your mother-in-law thinks; you can't control that/her; she's going to do her own thing regardless and if you pay attention, it is guaranteed to be upsetting to you and stressful for you.