First of all, welcome to the forum!
You said that you wanted to start with nature photography and later try weddings. Unless you're concentrating on macros (closeups), nature photography normally requires a telephoto lens, rather than the ones you mentioned. If you're including birding as part of what you want to do, you're probably going to need at least a 400mm lens and a 500mm or 600mm would be even better.
I have a Canon 30D and really like it, but the lenses that you mentioned are not known for producing quality shots. I tried the kit lens just to see if it worked and then sold it. The 17-85mm doesn't get raving reviews either. Here's a link to a review of it: http://www.photozone.de/8Reviews/lenses ... /index.htm
It might help us help you, if you told us more about the type of nature photography you have in mind.