I'd second what Dan said. Pick a small country, such as Canada, and do a quiet launch. Even if I get people to register their devices and join a beta distribution on TestFlight, it is still difficult to get real, workable feedback from them.

But if you launch in an App Store and make it very clear in your description and through in-app prompts that you're looking for feedback then you'll be able to iterate much faster. You'll also turn some of those early adopters into your most vocal advocates.

Once you've worked all of the kinks out of your MVP, and have validated your learning, a la Eric Ries, you can be confident that you've created something people really want.

One last thing: using the quiet launch as your beta will encourage you to ship this thing faster. The app ecosystem evolves so rapidly that I've come to believe that shipping an imperfect product is smarter than waiting for perfection. It's not until you hear from users that you know what perfection is anyway.

Hope this helps,
Austin