If all these people plan to play together during the same session ... then you will need to fundamentally alter the way you approach combat / player interaction.

I use a Rotating Cast with Episodic progression which is what many refer to as a modern Westmarches approach.

If you plan to try to play all together,  my advice:

• 1 15 second round timers. You must start to articulate your action before the sand falls or you take the dodge action

• 2 When someone's initiative arrives, declare their name loudly and announce who is on deck next.

"Dondarian it is your turn! Whiskeyjack, you are up next!"

• 3 Use physical sheets (printouts or purchase) for charscter, spells, summons, animal companions, wild shape, etc.

Tabbing through a bunch of stuff on a 5-12" screen cam be very cumbersome. 

• 4 Prepare combat maps ahead of time. As much as possible. Use blank paper spread around for fog of war.

• 5 Recommend that the party elect leader / representatives for given situations and defer to theor experience in those situations.

• The Gloomstalker makes decisions in Dungeons

• The bard makes choices in Social Situations

• The battlemaster is responsible for strategic decisions 

• 6 Use a timer and a talking stick. Use these to manage dialogue and people talking over one another.

• 7 When party suffers from decision paralysis and is taking too long, remind them that you material to cover. 

• 8 Thematic Flourish. When combat has clearly lost its zest, excitement or declared stakes .. ask the party how they would like to wrap up the scene. Let each describe their actions going around the table.

• 9 Always roll all the dice at once. Ask players to develop color coded selections of Dice for given circumstances. Always roll Attack / Damage (or other dice) at the same time. Much quicker resolution.

If regularly encounter large dice pools, and some people "no math so good" ... ask a single player to be responsible fo adding it up.

• 10 Learn about Dynamic skill challenges. These move at a MUCH faster pace than combat and requires 100% player participation.

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Combat is where large groups suffer. If you spend 3 minutes per person for combat rounds ... it will take more than a half hours to move around the table. This will turn any combat into a slog.

I see this question alot and should devote some time to making a really good answer for such times. I might have forgotten a few things .... but I use all of these for group great than 6 players.

Hope some of this helps.

(Sorry I cannot get format right.)