If you want to hear individuals clearly, they each need to be mic'd seperately. Anything else is going to make whoever isn't wearing a mic sound distant....that's the facts.
Groom wears one, bride won't be heard very well....Pastor will sound distant as well
Pastor wears one, bride and groom are gonna sound distant.
So, the correct solution is going to require some sort of a small mixer at the camera to get all those inputs down into one or two channels. Alternately, if you're doing a muti-camera shoot, put one microphone on each channel of the cameras and mix it when you edit the footage down later. With a two camera shoot that would give you 4 channels of audio to play with. You just have to be careful of sync'ing the footage from the two cameras up to avoid the dreaded lip flap.
If that is beyond your budget or capabilities, you might want to try and find a place close to where the pastor, bride, and groom will be actually reciting the vows and place a mic there. Not quite as good as having everyone mic'd individually but workable.