A friend of mine has suggested to me several times just to tell people we are thinking of joining a cult that doesn't allow children, I have not tried it yet but am seriously considering it for something different or to see the shocks on their faces... lol

You could always ask them if they would like you to call them ever time your BD'ing so at least they know your practicing.

Another one I like is "When the bank calls and says we can afford it"

or you could simply say "Oh are you offeringto be my surrogate".