They could engage in pretend or physical play. Whatever they decide to do, encourage your child to stick with it. Don't force him to do something that he doesn't want to do, but help him expand on what he is already doing. I see that you were pretending to be a fire fighter with Jana. By helping your child to elaborate on his play with other children, you are helping him to learn to build relationships with other children.
Children can learn a lot from discussing things that they have seen.
If they need help getting started, you can help spark the conversation. You can even start by telling the children your favorite part of the movie. Help support them by providing materials or helping them think of ideas for their play based on the movie. It can even carry over to the next day. All of this will help your child learn to sustain interactions with other children.