First of all let me just say that your wife has made an amazing accomplishment and that I think it is terrific that you are reaching out to think of something amazing to reward her with.
I can think of something that would cost too much money, if it is possible for you to get out of work for a day without her knowing.
You could clean the house, do laundry and dishes, so there is nothing she needs too do. Get just enough flowers to make a petal trail to the bathroom. In the bathroom, set up aroma therapy candles and draw her a bubble bath. After the bath, give her a message with a calming oil. Make or order a healthy dinner for the two of you. If you have children, get a babysitter. Rent her favorite movie or if she's not the movie type, take her dancing or something like that. Just make sure that she doesn't open her own door or pour her own drink or anything all night.
Tell her that you know how hard she's work to get to where she is and that tonight is her night off, she's not going to do anything but be pampered like the queen she is in your heart.
I'm a total sap and I would just cry if my guy did that for me.
It is memorable and not expensive, but very touching.
Good luck with whatever you do!
