One of the biggest issues you'll face with large numbers of players is access to the mobile device. Play with a large phone or a tablet if possible to ensure everyone can see the screen when they wake at night.
The Mayor should always push the device to the center of the table after they have chosen the Magic Word.
Playing on a long banquet-style table is more difficult than at a larger round table; if all you have are banquet tables, push two together so you don't have any players at the "ends".
If playing with the Doppelganger or Speedwords, some players may need to reach the device during the Night Phase. With a large group, have the players stand up through the Night Phase; this allows the players who have to reach the device to do so without accidentally bumping the table or otherwise exposing their identity accidentally.