Pick the gate first
A park can have several entrances with different approaches. Share a specific gate and check current access information before asking friends to meet there.
Choose a modest circuit
Start with one path section and a place to sit. Make a longer walk something the group can choose later rather than a condition of joining.
Return to a known point
Use the same gate for the end or tell everyone about a change before leaving. Save the last walk to the stop as part of the outing.