Kiosk Mode

This does not yet exist, with enough requests for it might be built at some point.

Could you not just create an account under your site and just log that user into a tablet?

The hesitation with technology is mostly laziness, we hear this all the time from hosts but those same people are happy to bore you with a thousand pictures of their pets so no matter how easy you make it, it sometimes does not matter. Most hosts simply tell singers/requestors that the app is the fast path and manual or "old-fashioned" requests get lowered priority. Harsh and is not always an option but after a small period of time, the location/venue will get onboard.

Also, the QR code/NFC tags are for convenience, they just link to your URL, there's no way around this unless you want to register your own domain name and simply redirect it to your URL.

You don't want to log in "yourself" meaning, your host account but you could create another plain user account. The only problem there is that it remembers the name that was last used so you might end up with some requests that have the last requestor's name on it because don't pay attention.

I need a simpler solution for older people (retirement community 70–80-year-olds).  It's once every couple of months so there's not a learning curve per say. Also, I don't quite understand what you mean by "Could you not just create an account under your site and just log that user into a tablet?"  

Meaning you could create a user using an email address or social media account you control and just leave that user logged in on the tablet or whatever you use for your kiosk.