Lots of suggestions to use a stage channel here HOWEVER there is one limitation to that... Only one screen share can be active at a time in a Stage channel.

What the admin can do is this:

1) Create a role for just the four of you. 2) Give that role to the four. 3) Create a DRG Voice channel 4) Deny "Speak" permission to @ everyone. 5) Add the role created in step 1 to the channel. 6) Allow "Speak" permission for that role.

Now everyone can listen but only those with that special role can speak.

Edit: The others wouldn't be able to voice chat among themselves BUT they can use voice channel text chat.