Bite the bullet and buy one that you can use
If you are still wishing to do your presentations what you need is a functioning goto mount, a six inch reflector will do the job, a camera, lap top, and a large monitor so everyone can see...and that way if the clouds run in you can run a movie of what you were going to display.
Have something for visual if you must but first timers wont see much even with a decent scope.
Good luck but if you are going to do it you must get serious John...
Alex