Put a disposal camera on each table at the reception, with a note underneath asking your guests to take pictures with it and leave it on the table at the end of the night so that you can see the wedding the way that they did.
This is a fun way to get children involved, because they love to take pictures. Also, this can keep guests busy that may get bored at certain parts of the reception. In addition, you will probably get a lot more actual candid shoots then from a professional photographer, since it is hard for not to notice them because of their equipment.
Undoubtedly most guests will bring a digital camera, but it may be a long time before you see those pictures, if ever. The disposable cameras will take the pressure of your guests to send you their own photos.
Some vendors also allow you personalize your cameras with names, dates, and so forth.