Christmas is such a hectic time for us humans, imagine what it would be like for a puppy who is trying to adjust to a new home. It would be really sweet if you bought puppy supplies (toys, brushes, bed, etc etc) wrap it up and give that to your wife. It still sends the message that she's getting the puppy she's always wanted for Christmas.
she'll get to pick out her own puppy, and the breeder can meet her, which is a requirement from an excellent breeder. Do check the YTCA breeder referral page. You can get a jump start on the research and have a few breeders on your list for you and your wife to check out.