Lee's answer is great.

What I will add is that in this type of setting you should be able to convey your product/service value add in one to two sentences. Then lots of repetition/reinforcement. Therefore don't stress about short prep time. Add simple visuals if possible and a concise, clear explanation and this will be best.

You are just trying to generate initial interest and word of mouth spread. Details can follow but the main value proposition should ring like a bell - that is what matters.