Unless there is contention between what the Miracast Adapter and Router, the router shouldn't be an issue. Miracast, WiDi (and all WiFi Direct Solutions) all use the modern WLAN Adapter and Modern OS's ability to create a Virtual WLAN Card for the connection, by-passing the internal network. So unless they Miracast Device is using a channel that is too close to the Routers it shouldn't be an issue.
I use a tool called inSSIDer for Wireless Site Surveys....
I use a tool called inSSIDer for Wireless Site Surveys....