Good luck with this.

I run an iOS-only app that Serves a small, specific demographic (and is free. It does not generate any revenue). It’s been shipping for a bit over two years, and has just over 1,000 users. I seriously doubt it will ever get more than a couple of thousand (a rounding error, for most folks around here). I did test it with 12,000 users, so it should handle the anticipated load.

I am writing the 2.0 version, now. I think I’ll add the “tap to connect” feature, and probably QR codes, as well.