Your 17-50 will be fine. Don't sweat that one.
Tips I can give would be to always support the camera. Tripod, monopod, set it on a railing. Don't think you're going to hand hold it and get good footage.
Shoot at 1/50 and 25 frames.
Don't use auto white balance! You'll hate yourself when it comes time to edit. Better to be off on the setting with a consistent color temp than to have it moving all over the place.
ISO noise isn't as important in video than stills so you can get away with using higher ISO if it gets real shady.
Audio is number one, even over the video footage itself. That's what is going to set your mood and tell the story. At minimum I would get full ceremony audio with a lav mic on the groom and get the toasts. You'll want both of those for your edit.
Bring more batteries and memory cards than you think you'll need. If it's your first video gig you will most likely shoot three times as much as you'll need.
Most important, get some practice in! Doesn't matter what you're shooting, just go shoot video. Note what you did and how things were set and learn it. Most of the still shooting will roll over to video but there is a lot of new with it as well.
And most most important, have fun with it!