I would like to show my DVD to an audience as a presentation. There would be more than 100 people present. Or do you know any other approach to solve this issue for me?
Buy a $34 DVD Player?
iTunes does not handle DVDs directly.
If this is a home made DVD you need to convert it to an AppleTV compatible h264 format.
One of the simpler options is the open source Handbrake application. You cannot replicate any menus in iTunes however.
Other options include MPEGStreamclip (free) but that will require Apple's MPEG2 quicktime plugin (about $20-$30 last time I checked).