This is my first post on this board, but I think I can offer some suggestions for your presentation.
First, you might want to think about the overall format of your presentation and tailor it to your expected audience's experience level (or simulated experience level, who is your audience?) For example, your first order of business shouldn't dive right into what a circuit is (traffic pattern over here in the US). Start with some kind of introduction, I usually try to answer the question, "Why do I need to know this?" Spend a little time introducing them to the subject, tell them what they'll be learning about and why they should care about it. Take a minute at the end and reemphasize the important points to conclude the presentation.
Explain terms where necessary. For example, don't assume that a student knows what demonstrated cross-wind means. Explain that this isn't necessarily a limitation, but just what was actually demonstrated. Relate it to personal pilot ability.
Don't try to explain everything in one briefing. Go-arounds and wake-turbulence both deserve more attention than you are giving them here, so might be best to just briefly touch on them but mention that you would give them more attention in another briefing.
How far out do you want to be from the runway on downwind? How do you know you are the correct distance?
You may find it helpful to practice in front of a mirror, or enlist some friends. Recording yourself is also very helpful, you may discover that you say "Ummm" a lot, or something of that nature.
Whatever you do, DON'T JUST READ YOUR POWERPOINT SLIDES!!!!! Your audience can read, and it is VERY BORING to sit through a presentation where someone is just reading slides to you.