A man and two women are walking down a wooded path, the man is pushing a young child in a three wheel carriage.
A man and a couple of women take a walk.
A man and two women is a man and a couple and one scenario take a walk while the other is walking meaning the same thing.
Two women are a couple while "take a walk" is synonymous with "are walking."
There are a couple of women because there are two women.