JAWS vs Voiceover

I teach visually-impaired students and made a presentation for them. I checked it for accessibility and was at home so I used NVDA which is similar to JAWS. Everything worked fine and then when I came to work and had the students access it on an iPad, they could not click on any of the buttons with Voiceover. Was there something else I needed to do? 

Also, is there a way to detect if a screen reader is being used and have it play media if there's no screenreader? When I use audio and the screen reader is used, they talk at the same time. I've adjusted the timing but it's too much audio. If there's a way to do this, please let me know.

Thanks.