Instead, I've come to rely on the two strengths that after 22 years of speaking in front of crowds (and that includes kids) I've finally recognized: 1. I am passionate about the things about which I speak. 2. I have a knack for being able to use striking media that resonantly illustrates my ideas.
I am expressive in different ways when I speak to teachers, parents, or kids. I'll use hand gestures, drastic intonation, and movement around a room to show my sincerity and excitement about my points. No one can deny my passion, but I follow-up my talk (and it's usually brief talk) with a short video or series of pictures and images that "speak" to my points. I like using movie clips or inspirational videos that resonate the theme of my talk.
Find your presentation strengths. Don't try to be the speaker you're not. Hold sway over the crowd however you can, and you'll get your point across just as well.