The surprise was your first mistake. Your second mistake may have been not going back to the bedroom to change before the event. While a kilted outfit and lifestyle can be fun and exciting, it probably rubbed salt in the wound for your wife to defend her husband to others when she didn't like the idea in the first place.

For your sake, explain to your wife why you want to wear the kilt (then tell us!). Make her a part of the process, not a bystander. Tell her what the tartan means to you, why you wanted to surprise her, etc. At the very least, she should appreciate the explanation, despite its tardiness.

Good luck, and I assume you may be a church-going family, so maybe you can show your wife this: http://www.youtube.com/watch?v=fxvQZbEOX9g