Congratulations to your son!
I have no knowledge about the specific impact of receiving that award but it’s something that Emory admissions would certainly know about.
It would make a nice why Emory essay topic to the extent it brings in your son’s interest in screenwriting, Emory’s strengths in that area, what he submitted to the contest, etc.
Officially, Emory takes the position that it doesn’t give weight to any applicant’s expressed interest in the school. However, year after year, Emory accepts a much higher percentage in ED1 (different from ED2) and a significant percentage of each class is comprised of ED1 applicants.