Q: "An older man in a baseball cap" Does this mean that "The man wore a cap."?
A: yes

Q: "A boy waiting outside the kitchen holding his bike." Does this mean that "There's a kid with a new bike."?
A: it is not possible to tell

Q: "A group of people in a sack race." Does this mean that "A group of people in a sack race during a family reunion."?
A: it is not possible to tell

Q: "A man and a woman are sitting on the grass." Does this mean that "A man and a woman are having a picnic."?
A:
it is not possible to tell