My friend is Coptic Orthodox. He thinks that going to a theme park is a waste of time and money. I offered him a free ticket to come with me to the theme park. He says that the money that is spent on tickets should be better used donated, even though this particular place has many charity events, scholarships, job opportunities, etc. What should I tell him to convince him to join me?
You should not try to persuade your friend to join you to an amusement park, but rather be grateful that you have a principled friend. Sometimes, people put activities in two categories: sin and not sin. This is a minimalist approach. Not only should we avoid committing sins, but we should also strive to grow in virtue, spiritual maturity, faith, discipline, morals, and charity. One must consider how an event or activity will edify and enhance his or her spiritual life: "All things are lawful for me, but not all things are helpful; all things are lawful for me, but not all things edify" (1 Corinthians 10:23). Your friend does not value the activity you mentioned the same as you according to his principles.