Proof-photo prompts work because they answer what counts as done before the group starts. That clarity makes sidequests easier to complete.
Prompts for walks
Use best patch of sunlight, proof you took the long route, a sign nobody has noticed before, or the view from the halfway point.
Prompts for food plans
Ask for the receipt, the first bite, the menu item everyone debated, the table photo, or a one-sentence review from each friend.