Juvenile? I thought that was some good advice! Congrats as well to youself and good luck to your bride! Also look into renting, if that hasn't been mentioned, before purchasing, the more formal things you probably won't get much use from. (The jacket, the frilly shirt, etc won't come in as handy down the line as the kilt itself and hose if you don't attend any formal do's.)

I would wear underwear on your wedding day- especially if your altar is any steps up above the crowd- and since you're not a usual kilt-wearer. There's a whole thread on underwear choices here if you want more help on that. I'm sure folks will disagree, but having been to a few wedding receptions, the crowd can get kind of raucous.