I'd be curious why you'd recommend an AppleTV over a lightning-HDMI adapter. When we demo our iPad apps the direct connection is perfect. Spotty, shared wifi can hurt Airplay sometimes (and yes, it is awful that it uses a Wifi connection...)
Agreed. I've seen countless demos bungled because they required WiFi and a big crowd came and took out the WiFi. You should always have your own 4G LTE hot spot so you don't depend on site WiFi, but they you still want to keep everything local or over cables that you can.