I think that there are several points to consider if you are inviting people for a demo or indeed being invited to do a demo

1. Who are you giving the demo to? If in the case of the op it's just a small panel of other teachers then does it really simulate a classroom experience? No

2. If it's the case of it just being delivered to a few panelists then do you really need to be in the room with them. Surely they could have hooked up a webcam and done it over skype.

3. You're right to say that it's easy to deliver a demo class but does that necessarily prove you as a teacher who is able to develop students over a period of time? No, anyone can put on a show for 30-40mins.

Solid references from established institutions (which an experienced teacher would have) should be enough.