These are digital pictures, and the photographer always takes more than one, so I really don't see the big deal. I really don't care for posed pictures, anyway. We make photopass photographers nuts because we don't like to "assume the pose" when we are in front of their lens. We want to look more natural.
All of our best pictures have been taken when the subject had no idea that someone was about to shoot, and a few of the funniest include someone other than the intended subject. As long as the photobomber isn't being vulgar, I see no harm.
OK - two opposite opinions here. I made the point that the photo could have been retaken in 30 seconds (if not sooner). They are digital and any "interference" can easily be solved by a simple "let's do that one again, shall we?!"
But, an intentional photobomber, no. There's no excuse for that. Not at all. But the OP's husband was not an intentional photobomber. That's just plain rude, in my opinion.