As other posters, simple activities for the children, I get the older children to hide chocolate/sweets in the garden then treasure hunt, pens, pencils, dvd at the ready. Coats in a bedroom.
Food: warm nibbles to pass around, cold buffet food on table. I do cold pork/ham (roast the day before) two different salads, dips and crudités, smoked salmon, cheese board, bread and pate. Could you borrow knives and forks from someone? Warm food, pigs in blankets, supermarket pastry nibbly things, garlic bread, etc. You could do bread and pate bite sizes, quiche, pizza, smoked salmon blinis and sandwiches if you don’t want to use cutlery. Leave a cheese board, fruit, bread and crackers on a table for people to help themselves.
Drinks: first drink we serve, then it’s help yourself or dh goes around topping up glasses.
Tidy up but don’t bother deep cleaning (apart from toilets/kitchen), no one will notice and you’ll just have to do it all again once everyone has left. Make sure you have plenty of toilet roll, spare wet wipes for toddlers and turn the heating down. I have no ideas about how to get people to spread out, people naturally gravitate towards the kitchen in our house!