My family is invited to a Wedding at a Trump Golf Course at 5PM and the dress is semi-formal. What is appropriate for teenage boys to wear?
Technically, semi-formal means a suit and tie. Many teenagers are still growing, therefore parents do not want to invest in expensive suits. Fortunately there are stores such as J.C. Penney where you can find nice suits with coordinating shirts and ties for a reasonable price. I am not familiar with the location you have inquired about, but even if the wedding is on an actual golf course, semi-formal is a suit. My other recommendation is for you to call the bride or groom and ask what they would like the teenagers to wear. At the very least, I think they would request a jacket and nice pair of slacks. If the teenagers don’t want to wear semi-formal they can choose to stay home. It is distracting to see young people underdressed at special events.