I did this at my wedding receptions and it was very fun!
Buy the one time use cameras from Wal-mart or wherever you shop most! Print address size labels explain that they take pictures of whatever just leave the cameras on the table at the end of the day! Put the labels on the backs of the cameras and leave one on every table or just a few tables! Let your guest pass them around! It lets them have something to do While your mingling! The Kids LOVE THEM!
There is a warning in doing this Though! Like i said KIDS LOVE IT! There will be some pictures that won't turn out and a lot of people don't know how to use a flash so they may be dark and blurry!
However I had some pictures left over on several of the cameras so we used them on our honeymoon!