ecosse,
If your wife bought the trial lesson, and wants to fly, than you'd better take her. Otherwise, tell her to meet you back in an hour, and photo you as you get out of the plane. You are paying lots for the experience, don't dilute it by having your loved ones in the back. Take them later, and show them what you have learned, and your confidence.
If you have a scare, will your wife ever be happy again that you are flying? If she does not like it, and wants down, do you want to cut your flight short?
The ear to ear grim you'll have for days is enough for her to enjoy for now. If she simply MUST go, have the instructor take her for her own circuit.