Anyway...basically - what everyone else said!
Your DH needs to get that his priority after this LO is born is to protect you and the newborn and help your family settle in, adjust and establish important things like breastfeeding. Everyone else and their burning need to satisfy their own curiosity can wait. Seriously, the way people treat post-partum moms these days bugs the ever loving crap out of me. It's all about their need to see the baby and your responsibility to be hospitable and sociable after you push a small human out your girly bits.
Someone else advised getting your in-laws on board with keeping things under wraps and I think begging off on 1) establishing breastfeeding and 2) giving your DS time to adjust to the baby is a really great way of approaching it.
Other ideas - 1) if you're delivering in the hospital, make sure you have the nurses put it in your chart (and make sure the nurses station knows) that you do not want any visitors. Leave them a list of names you'll be willing to see and tell them anyone else should be told to leave. This is one of the reasons why I typically don't even tell my family I'm in labor until after the fact...When DD1 was born, we made the mistake of telling a couple from church (we *thought* at the time they were our friends...that friendship went south in horrific ways later, but this should have been a hint of how weird they were) - these people SHOWED UP AT THE HOSPITAL like 30 seconds after DD1 was born. To this day I am not even sure if my vag was covered. It was insanely inappropriate and creepy and we could not get over how weird it was....But what was really amazing was the nursing staff just let them into our delivery room (we hadn't even moved to recovery yet!!). So for DD2, we put it in our birth plan - NO VISITORS. And we went home after 24 hrs so, there wasn't much time for pop-ins anyway.
2) Change all of your voicemails to state something to the effect of - we just had a baby, we are busy recovering and will not be entertaining visitors for a week or so. We're so grateful for your kind wishes and we cannot wait to introduce you to our new LO and we hope you'll respect our privacy as we take a wee bit of time to recover and rest.
3) Start warning people in advance. Tell people you're planning on laying low and not entertaining any visitors to make sure you have time to heal and make sure especially that DS has time to adjust to having a new sibling. Some people will respond better if you've given them some advance notice that they're NOT WELCOME at 3am the day you have the baby. ;-)
Other than that - I know it's hard, but try not to feel bad. What you're hoping for is not unreasonable, it's the way our culture treats post partum moms and babies that is outrageously unreasonable (Dear everyone: for once, this is NOT ABOUT YOU!!!). I'm guessing you'll be able to find a way to communicate your need for privacy and quiet to your DH to get him on your team.
I don't know....this one issue makes me kind of glad we have such distant relationships with most of my family...I mean, I would love it if they were the people I want them to be (nice, supportive, etc)...but I do feel grateful that at least most people we know are quite content to just leave us alone after the birth of a LO.
ETA: I didn't think I'd be able to find it, but I always liked this article on post partum care in America