The most effective change to introduce dramatic irony in the story rewritten as a play would be D: Josh would plan the event to honor Coach Wilkins as a surprise party during a scheduled team practice.
This change creates dramatic irony because the audience would know that Coach Wilkins is unaware of the surprise and the effort that goes into the event planned by Josh and the team. The tension would build as the audience anticipates Coach's reaction when he finds out, especially considering how much he has meant to them. The contrast between the team's intentions and Coach Wilkins' potential surprise or emotions once he realizes the honor being bestowed upon him adds depth and engagement to the narrative.