Open the windows every hour, to air the rooms.
Only one person serves the drinks (no passing the bottle)
Only one person hands out the presents
No touching the “finger food”… use cocktail sticks or similar
Elderly or At Risk… sit at the end of the table with 2 empty chairs between each of them and between them and other guests.
Keep well distanced
Masks worn except at table
Use the Tous anti Covid app
I’ve also read that families could bring and eat their own nibbles… so no risk of cross-contamination .
also suggested to keep the time spent at table … to a minimum … and, whatever, make sure everyone is seated well apart from each other, spread throughout the rooms if necessary…