This is super cool and would be awesome for situations where your guests are familiar with QR codes. But from my experience the process would go something like this:
Visitor: What's your wifi password?
Me: No password needed! We have a cool QR code you can scan that will auto-join you!
Visitor: Oh cool, how do I use a QR code? Do I need an app?
Me: Nope, just point your camera at it.
Visitor: Like .. .take a picture of it? And then what, do I...
Me: No just point your camera at it.
Visitor: Ok let me try it ... oh cool it's prompting me to join your wifi network? what do I do now
Me: Yes Yes, just proceed, that's what it's for.
Visitor: That's soo cool, thanks.
Vs
Visitor: What's your wifi password?
Me: ShinyTortoise78
Visitor: What's your wifi password?
Me: No password needed! We have a cool QR code you can scan that will auto-join you!
Visitor: Oh cool, how do I use a QR code? Do I need an app?
Me: Nope, just point your camera at it.
Visitor: Like .. .take a picture of it? And then what, do I...
Me: No just point your camera at it.
Visitor: Ok let me try it ... oh cool it's prompting me to join your wifi network? what do I do now
Me: Yes Yes, just proceed, that's what it's for.
Visitor: That's soo cool, thanks.
Vs
Visitor: What's your wifi password?
Me: ShinyTortoise78