We went to one which was around lunchtime....they had a caterer do a spit roast type meal (with desserts) and they had a small marquee just incase of bad weather and a jumping castle for the kids.
It was a wonderful relaxing day just as they wanted and they only had a friend do a few 'offical' family photos and the rest were just friends capturing the day.
Most of the guests changed into 'relaxing' clothes towards the end and it was just a beautiful day.