If you're not using facebook events you're missing out
One app that people are constantly on, even if they hate being on it is Facebook.
Unfortunately and fortunately, facebook is very addictive. And you can use this to your advantage.
Get a Facebook Business Page and Add events to that facebook page. People who like your page from their personal page will get notified of your business event. And also people who are close to your or have the same interests as your business will get notified of your event.