I agree with xStep here. All the wedding videographers are advertising HD nowadays. You'd be at a distinct disadvantage if you only shot SD. More and more folks have HDTVs now and want/need/expect HD wedding videos.
As for the camera ... I don't think a HF100 will cut the mustard either. Sure, it's HD, but it's a consumer camcorder. I don't know all of the specs, but does it have a mic-in port? How about a hot-shoe. I'm also not sure about using SD cards. I'm sure there are other features that you'll need to make pro-quality wedding vids.
If this is for a business, then you might want to look into a pro-line HDV camcorder. I'm no pro, but I do know that in the wedding industry, image counts for a lot. The bride will likely interview with several videographers. She'll see guys with the huge pro cams and compare that to the tiny HF100 and think "gee, size matters, right?". 😉 And since it's a business, you can write it off as a business expense. Equipment gets depreciated over 7 years, right?