A quick trip to the site seems to indicate these are not competitive Spandex sorts but folks with a lifestyle view of cycling. After having more than a few conversations with similar-minded people I would recommend orienting your presentation around improving the cycling experience they already enjoy rather than presenting ebikes as an alternative. You might even title your presentation something like
"ebiking: enhancing the cycling experience". This is upbeat, gives focus and direction to the discussion, and starts off with you squarely on 'their side'.
You might start by clarifying the idea of partial assist while pedaling instead of 'either/or' 'pedal/motorcycling' which is the most common misconception that I encounter. Present it as riding a tandem with a stoker to help when needed - you still are pedaling but get some help to make the hard parts less burdensome. Just ask the audience if riding a bicycle-built-for-two means the riders are 'cheating' (looking for a laugh here...). Tell them ebiking is the same deal except you don't need to be married to the other rider or listen to the chatter. This part should lay the groundwork for making ebiking seem an extension of what they already like about cycling rather than a completely different experience - they aren't giving something up.
Next you might look at situations where ebiking can expand the normal cycling experience to provide a solution to difficult cycling problems. Here you are not confronting those who see ebiking as a threat or competion but rather are enabling those who would like to cycle but cannot. Mention some different cycling demographics where ebikes can assist: the folks who like to commute but need to arrive at work without needing a shower, people saddled with tough terrains, people who like to ride but are finding some old favorite routes more challenging as they get older, folks who would like to ride but don't because they're not quite up to it anymore or are afraid of some health issue (bad knee acts up, exertion) making the trip home too compromising, folks who just want to do local grocery or errand runs without an automobile, etc.
I would stay away from the 'motorcycle' type ebikes prevalent on ES and show what ebikes look like and make them more familiar. Present some pictures of Kepler's friction drive and his bikes - unobtrusive, low powered, inexpensive. Very 'cycling oriented'. Move on to bikes sold at federally regulated power levels and show some design options there, relating them to your previous demographics - the step throughs, cargo bikes for groceries, sportier models for just plain riding. Here you are trying to show the range of ebike solutions available so your audience can see things that might help them personally. A quick sequence of pictures here without a lot of commentary on each would keep the presentation moving while making the ebikes seem more familiar and revealing possibilities. And of course you point out the possibility of DIY upgrade to their existing favorite ride.
Once you have made the pitch to get them interested, you can move on to a bit of the familiar low level technical stuff, charging, range, controls, pedal assist, weight, etc. so they get a glimpse of the 'user manual' differences from a regular bike and what they might expect as problems/advantages over what they are doing now.
You can get into the technical stuff, but frankly I would make that a pretty 30,000ft view instead of doing a deep dive into 'service manual' stuff. Have some extra images/slides to flesh out these areas for the Q&A but don't force it as part of the main presentation. If there's interest, you will be prepared, but if there's not, folks won't feel overwhelmed with stuff they don't 'get' but assume they will need to know. (Here you are catering to "I want a red car that goes fast and I don't care how it works...").
Finally, you might get to law which is pretty much a downer and can be annoying to get across (Lord knows we still have folks on ES who insist the Feds limit ebikes to 20mph...). This is the 'restriction' side of the coin and it's likely best to avoid having the audience get that negative stuff in their heads too soon and detracting from the upbeat stuff you really want to convey. If your presentation runs long, this is the stuff that you can decide to cut or hurry through - it's not your main message about ebikes improving their cycling experience. If there's interest you can explain this in more detail in the Q&A. Importantly, for many cyclists, this low power stuff is exactly what they are looking for...
Anyhow - this can be done many ways, but your success will depend on getting the audience to see that ebikes offer them a solution or an advantage without losing the benefits of the cycling they already love. If you go in talking about 5kW motorcycles with pedals that can do 45mph, you will lose them before you ever get started because that is not their world view.
... just some thoughts....