I'd like to give a presentation to other people who happen to be in the same room. I'll be running various programs and would like my screen to be visible as I work. Instead of a projector, I am wondering if I can use screen sharing. It's not clear to me if there is a way I can start such that I can be absolutely sure there is no chance of others having any control over my computer, cursor, command-line, etc. I only want to broadcast my screen to other computers' screens instead of using a big monitor or projector.
How exactly can I set up screen sharing to be sure? Are there good alternatives within OSX? (I don't want to have to download or install 3rd party software).