We do this sometimes and it works well. We have a general idea of who is best at what, we request savoury from the cooks, sweet from the bakers amongst us and ask for some cheese and biscuits or fruit from the less confident in the kitchen. If it's mainly friends and family they will often communicate so doubling up doesn't happen. People generally bring a bottle of wine or a few beer cans. We supply the venue, home, garden or beach depending on weather, the cutlery and crockery, soft drinks, wine at half bottle per person and a few cans of beer per guest. We supply seating and tables unless it's a beach do when we ask people to bring a blanket or towels for seating. We have a good supply of folding beach chairs between us all after years of doing this.
Weather permitting we follow up with rounders and boules otherwise dancing once the dining room has been cleared.
I sincerely hope that your day is a resounding success. If anything is forgotten in the way of food, drink, entertainment, etc., laughter fills the gaps beautifully.
Have a lovely time.