I say definately suprise her. Although us ladies normally like to be prepared for things like this, once in awhile a great suprise is worth the unneccessary worry. Just reassure her that you don't really care if her legs are shaved and such, and she will be fine. Also, make sure that the kids are all set and comfortable in the clubs so she won't worry about them. It might be even better if you do the wine tasting, then go directly to the spa! Go for it!
Sue