Ewan Lamont wrote:
But can they be connected to Wifi and not be on the Internet?
That depends on the WiFi network. You can have a WiFi network that is not connected to the internet. But, it doesn't really matter in this case. As long as both devices are connected to the same WiFi network, regardless of whether or not the WiFi network is connected to the internet, and both devices have BT enabled, it should work.
I suggest you carefully re-read the articles that FoxFifth linked to above. They lay out the requirements quite well.