How much food do i need to do a buffet for 100 people?

I am looking to get friends and family to help make a buffet for my evening wedding reception. We are not sure what we need. we want to keep it simple with party food, stuff like chicken bits and mini sausage rolls. We want stuff that is ready made in bags and that just needs to be shoved in oven then served cold next day. does anyone have any ideas and quatities? thanks.