Follow up: told SD's we're preggers...

Thank you to all of your encouraging and helpful replies!  Breaking the news went great!  My DH went into their room alone and shared how they were going to be big sisters to a baby brother.  They couldn't have been more excited and instantly started going on and on about all they would teach him, could they look at baby name books?, etc etc.

I'm sure there will be little moments of insecurity along the way, but DH is so great about spending one on one time with them and doing his best to make them feel loved and special.  I'm so happy they responded the way they did, mostly because he had been so nervous about it.