Why not try some escalation dares, where you start with a simple task/dare and each of you in turn make it harder/more daring, or drop out. Last person in has to complete the dare to get a reward from the others, or gets punished if they fail.
For example, for a public escalation dare - agree first on a route/time to walk, then each of you can either:
- Choose a piece of clothing that can't be worn on the walk
- Add a task to do on the walk
- Extend the length of the walk
Or a painful dare - each of you in turn:
- Adds a clothespin to a specific location for the duration of the dare
- Adds 10 spanks to a bodypart of their choice
- Adds 5 rubber band pings to a location of their choice