Producing a play would be great but it would take up much time to practice and all. A talent show, I think, would be better. Students could display their talent using English as their medium of expression. They could sing, dance, orate, etc. If it requires an outdoor venue, you could have it in a park or a field where you can hold a picnic, like a day camp. Fill it with booths, decorate it with any theme that you like. Plan some games. Organize a treasure hunt.

Same as a small event, just bigger.

Why not have " an English market day" or fete to showcase your program, where students have to speak in English. Based on their interests, in groups of 3-4, your students can man various stalls where they explain what they are doing in English. Then people can go to various stalls that your students set up. Examples: food [ a typical English morning/afternoon high tea of cucumber sandwiches and cakes/scones with English Breakfast or Earl Grey tea , powerpoint presentations of speeches, debates, plays, students' choices of current English music, impromptu acting/ poetry recitals, books and magazines, posters about aspects of the English language. Someone can explain how to use italki [ you?] to learn English. You might even have a G& T[ oops, sorry, can't drink on duty] It was a nice thought. Maybe some of the kids can form a band on the day to entertain the public. It can be inside in your hall with long tables and in various rooms or outside in marquees depending on the weather. If it's outside you could have a cricket match:))))

Just an afterthought for your English Day. Consider asking your students to take photos of the events they were involved in/responsible for and write about them here in Notebook with a photo underneath.

It is very difficult to advise you on the organization of a major event, because in Muslim culture single men can not share space with single women. Then you'd have to organize two events: a great event for men and another great event for women. Do not you think?