Need a Recommendation for a FUN App to Introduce Sighted People to iPhone Accessibility

any of the audio games would work for this perpice since it would show them how to swipe through the games and stuff like that.

It's a very interesting puzzler that uses a lot of different facets of VoiceOver to work correctly and is quite intriguing whether blind or sighted. You could then have them see the screen as a demonstration of just what VoiceOver was making work--I've heard it's quite impressive visually.

Perhaps, something which didn't have a bunch of sound might be beter for a group presentation. Path of Adventure is inexpensive and easy to just start playing. Choice of Games has some free games in it like Choice of the Vampire. That would be easy to get going with using pretty much any accessibility tools. A card game like Sushi Go could work well. Shredder Chess is very accessible using vertical navigation on the VoiceOver rotor to help examine the board.
Going beyond games, perhaps an app like Terminology, Drafts or Day One Journal would be good demonstrations. They work very well with VoiceOver. Most public radio service apps are very accessible. The CBC Listen, BBC Sounds and NPR apps all work well and are good for beginners. You'd use the one relevant to where you were. Best of luck with the presentation.

Besides games letting them know about the app and how is helping with those who have issues with letters. Accessible app and is good.

Also showing the use of a app that sighted people use and is accessible will go a long way.

it's accessible and I think it's fun.