The best house-party sidequests are small enough to ignore and fun enough to join. They should add texture to the night without turning the party into a scheduled event.
Low-pressure party quests
Try best snack table photo, everyone adds one song, find the most mysterious object in the room, make a three-person toast, or capture proof of the first empty bowl.
Use proof as the recap
The proof photos become a lightweight recap of the party: what people noticed, what they brought, and what the group found funny.