My guess is that your head will be spinning by now. You have received some very good advice . . . and some very bad advice . . . and some advice that would take literally months of hard work and thousands of practice shots to learn. I don't think you have the time (June 1st is closing in quickly), and probably not the inclination to become a "pro" for this wedding . . . but you do have the time to learn a few simple steps that will make you look like a whiz as an amateur.

I shoot over 25 weddings a year, and have been doing so for over 40 years . . . that's approaching 1000 weddings. For many of those I had an assistant that I had carry a camera and flash to take extra shots while they were not assisting me with off camera lighting, etc.. I set them up with a few simple settings that allowed them to get consistent results with little or no previous experience . . . so I will share those settings with you.

1) I would strongly suggest renting a 24-70mm F/2.8L lens for the day. You will be in several different venues during the day, some of which will be such low light that your present lenses will be challenged to get focused both quickly enough and accurately enough to get consistent results. Even though you may not wish to shoot at F/2.8 . . . your camera does have to see to focus. Especially with flash, when you zoom in with your variable F/stop lenses, you will be limited to the F/6.3 ability of your lenses at longer focal lengths . . . your flash results will suffer and ambient light will be non existent.

2) Far more important than "bokeh" . . . which is a subject tossed around far to much for wedding photography . . . is having lots of DOF (depth of field) for multiples of people at different distances from the camera. Let's work on getting both the bride AND the groom in focus, and if we are lucky, it would be nice to have some of the bridal party in sharp focus as well. Bokeh be damned!

3) For you, as the chosen one, your most important assignment will be to be at the wedding rehearsal. This is where you get to know all of the most important people that will be attending the wedding. This is where you discover the events that will take place during the ceremony, where you can be to get the best shots, from what direction the groom and groomsmen will be arriving, which aisle will the bride and her dad be coming down, how fast the bridesmaids will be following, where to be when the bride kisses her dad with tears in her eyes, etc, etc, etc.. This is also when you get your test shots of all the challenges that the ceremony offers. BE THERE!

4) Someone suggested the Lite-Scoop flash modifier . . . good choice and before you order it, watch this video.
http://youtu.be/-qR3owdOM6U
I've seen many a photographer using it incorrectly because they either didn't understand, or never bothered to read the instructions. I never use my flash without the Scoop attached.

5) Camera settings . . . only two to remember . . 90% consistently perfect exposure. If you wonder why you need to use any of these settings, please ask. I don't want to make this a book. :-))

Indoors . . . camera set on manual . . . ISO 400 . . . Shutter speed 1/200th sec . . . aperture F/4.5. (**** If your lens will not stay on F/4.5 throughout it's zoom range, limit the range of the zoom that you use or rent a constant F/stop lens)
For real close ups or long shots change your FEC (flash exposure compensation) accordingly. With Lite-Scoop start FEC set at + 2/3rd stop.

Outdoors . . . Camera set on TV . . . Bright day (sun, hazy sun, beach, etc.) ISO 100 . . . dull day or dusk ISO 400 . . . shutter speed 1/200th sec. . . . flash on TTL with FEC set at -1/2.For real close ups or long shots change your FEC accordingly.
With Lite-Scoop start FEC set at +-0 stop.

Do not use AV or P setting on the camera when using flash. The flash will limit the shutter speed to the sync speed when outdoors and will cause massive overexposure. Indoors it will slow the shutter to a slow speed that will cause camera and subject movement blur enough to ruin many images. High speed sync is OK to use outdoors, but not for an entire wedding as it will overheat the flash, use too much battery power, and limit the total power of the flash.

Back up equipment is a good idea. Too many flash and camera batteries is a very good idea. Lots of memory cards is a must . . always have more than you need . . and four 8GB cards are a better idea than one 32GB card. Don't keep them in your camera bag, keep them in your pocket where they can't be lost or stolen.

When in doubt . . . shoot it . . . the cake, the candle, the place settings, the flowers, the rings, anything . . . you can chuck it later, but you can't shoot it later.

Have fun and enjoy the wedding. Sit down and eat with them . . . nobody should have their picture taken while eating anyway. Ask to be seated where you can shoot what's going on at the head table. Give your extra equipment and camera bag to the DJ to watch for you. It's big business dressing up and stealing photography equipment at weddings . . don't be a victim.

Good luck . . . you're braver than I! :thumbup: