I think your answer depends on what you're prepared to do, in terms of child care. Are you going to keep your kid in daycare no matter what your wife does or says? In that case, I might tell her, but of course I don't know the specifics of your household. I might tell her when he (your son) was not around, so you could get it out in the open, and not be tempted to a) keep him home and b) use it as a manipulation tool (I don't mean that as harsh as it sounds). But if you're going to tell her and then change your mind, don't tell her. Why bother? Because then if he stays home, she'll see that as a victory, as you giving in.
All that said, I wouldn't let him stay home with her, were I you. You're his dad, and you're supposed to protect him. Sad that you have to do so from his mom, but it is what it is. But I know you know all that - otherwise you wouldn't be asking the tough questions. You're doing great.
I wish I had "people" I could call into action
