If you are doing it just for fun I would suggest you bring a tripod, a small external flash, and a wireless flash trigger, with a good fast prime. Then be unobtrusive, but engaging with your subject.
The other thing I would suggest you is to look online for model poses (people generally don't know how to pose, it is good if you have ideas and can give them tips, but it won't work if you tell everyone to do the exact same thing. Unless you do it as a gimmick, in which case it could be cool). There are many websites specializing in wedding photography, you have forums, blogs, that give all sorts of advice. It is also great if you know the venue. That way you can plan your shots ahead of time and bring the equipment you will need for them, instead of lugging around a lot of stuff just in case.
Best of luck!