With all due respect...GET OVER IT!
I have children, two of them, and you know what family still "intrudes". Let's face it, anyone who has family is faced with all sorts of "what will you do next questions".What you don't realize is that those of us with children get asked if we'll have more and why or why not CONSTANTLY and with children also come all the other little tidbits of "advice" about what you should or shouldn't do...breastfeed or bottlefeed, homeschool or ps, spanking or not, etc. As far as I see it childfree couples have it easy in this regard because at some point when you get beyond childbearing age, you won't get the comments anymore. Those of us with children will have to listen to other peoples' opinions for a lifetime. I say take it all in stride and if someone does it out of spite than you got bigger problems with that relationship than the nagging.
Er, you don't have to do any such thing. You can grow a spine and inform them (as subtly as you like or as firmly as you must) that the matter is none of their business.