For your wife's sake, if it's only been recently that you've started missing meetings etc., it might be wise to wait before drawing an official line in the sand. It may be that in time, the JW's in your life will get the picture and back off. If enough time goes by and you play your cards right, you may be able to have the best of both worlds in terms of not being shunned every time you see a JW and having your wife be the object of pity in the congregation. You can send a DA letter in at any old time if you choose to later....why not give fading a try?
You shouldn't have to strategize in order to leave a religion but it is what it is....a cult or at least cult like religion that you've / we've managed to get tied up in. I don't know your situation but for me it was best to little by little fade out and not play the game by their rules by sending in a D A letter. Who are they anyway that I should bother giving notification?? The relationship with God that you once believed in as a JW, was supposed to be between you and him. You don't need to explain anything to anyone. Just vague non committal answers (if that) should keep them off your back. Tempting as it might be, there's no need to give them a piece of your mind spill your guts, explain or justify your personal beliefs to any one of them.