Expect you will have fun with this. Would recommend renting/buying a backup body even if only so you can have two lenses mounted all the time. It is hard to get the shot when you are changing lenses. For an outdoor shoot you may be wanting more firepower than the 600EX can bring to the game. I find that Einsteins paired with battery packs are a good choice for me. If no assistant is available to hold the lightstand(s) then make sure that you weigh them down very well!As an alternative you could gang together multiple 600EX units. Financially the strobe and battery pack costs far less and will up your game in other situations down the road.
For lenses the suggestions above all make good sense. The only thing is you need to match the lens lineup with your shooting style. I know it is hard to nail that down without the lens options on hand to determine what your preferences actually are. It wouldn't hurt to rent them for a weekend or two beforehand and get familiar with what they can do and the look that they offer. The better you know them, the more confident you will be in getting the shots you want on the wedding day.
Good luck and have fun with it!