Preventing any interruptions without locking the meeting.

Hello, is there tried and tested procedure for preventing any unwanted interruptions during a meeting, without having to lock the meeting. I want people to be able to enter the meeting anytime they want (no waiting room) and even leave anytime they want, but NOT interrupt in any way a powerpoint presentation that I will be giving. I need assurance that the act of people coming and going will not remove the focus of my mouse slide advance  - I'm using a Kensington wireless clicker. And of course I need no have zero noise from participants and I don't want anyone else picture from appearing over mine. My current thinking is:

Spotlight for Everyone, Mute All, Mute All Upon Entry and untick 'Allow Participants to Unmute Themselves'. 

Is this correct or is there a better way, have I left anything out?

Thank you in advance!