Hello Emma,
That looks like a great talk, it's really nice that you had the initiative to put it together and go and present.
From what I've seen, many questions from newbies are related to GIS as science, rather than being software specific. Those are questions related to projections, vector vs raster, file types (int, real, text, etc), scale and surveying issues, etc. I think for new people it would be great to remind them that many tasks are simple to do in QGIS, but more advanced tasks sometimes rely on a good understanding of the theory behind it all. And that's maybe a good way to help others understand what sets GIS professionals apart from simple users. If it all had to be condensed in a bullet point, it would be something along the lines of "understanding general GIS theory (projections, data types, file formats, etc) will help you loads!".
Good luck with your presentation.
Cheers,
Juan