When you have a group of characters that are together throughout a majority of a movie, or even just a bunch of consecutive scenes, it’s fine to refer to them collectively: “The four of them walk to the building.”

If intervening scenes don’t feature the group, it’s a good idea to mention the characters each by name remind readers who is part of the group.

When dealing with a large and well-defined group — such as a football team or a show choir — it’s fine to refer to them as a group. Readers will assume the whole group is present unless you specifically exclude someone.