I've been in a similar situation and the feedback I got from everyone here was to be open and honest with your wife and absolutely do not hide anything from her. I took this to heart and it's sound advice. I convinced my wife to let me get another gun, after many discussions (and debates), and came home with a Winchester 9422. The caveat for me, however, is that I keep it in a gun safe, which I managed to get for free from a relative.
with that said, I know you don't have any regrets making the purchase but you have to put yourself in your wife's shoes and see where she's coming from. You've got two little ones in the house, plus, your wife doesn't sound too thrilled about guns. Also, you didn't mention if you even have a secure place to put your guns. I dunno. If I were your wife and I found out you made a large purchase that happens to be a gun, i'd be pretty p*ssed off. you made an impulse purchase, which believe me, all of us can relate to, but you did it at the expense of the trust between you and your wife