Xort and Calabego are right. You need to make sure your wife has a totally excellent experience the first time out or you are in trouble. What I did was go take some lessons myself, get certified and then take her on an easy charter with just us and our sons.
My brother in law had a sort of combined approach - He chartered a boat in the Bahamas with a captain who is also a certified ASA instructor - After a week he had his bareboat certification (he wasnt starting from zero) and his wife had 101. Now we are all (me, my wife, her sister and brother in law) going to Belize to sail around next week. My brother in law and I have been scheming and planning to get the girls addicted to sailing - making SURE they have good experiences is key - and not rushing anything. They will learn just by being on the boat and taking the wheel and seeing what happens when you tack, etc. Now my wife has said she wants to take some lessons on our new-to-us boat without me aboard. I think the good guys are winning!