ummmmm.... you know, to tell people is entirely up to you. nobody has a "right" to know anything personal about
your life at all unless you choose to tell them, but then you risk the possibility of judgement!
i'd let your friend get re-aquainted with you and your wife and see how things go. if time goes by and it presents an "issue" then your friend will have had all the positive "stress-free" time with you and your wife beforehand so that they know that you are good people. does that make sense?
so, no i wouldn't say anything - not b/c you are hiding or have anything to be ashamed of, but because it's nobody's business. maybe down the road even if there never is an issue, you could let them in on it, but only if you feel comfortable and you know that this person will still be a friend even after knowing what is going on.
"Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did do."
-- MARK TWAIN