I've taught more seminars than I can count. Second question to ask yourself (after "how much do I get paid?") is "what do I want the participants to get out of this?" That's usually a list rather than a single answer; for example, you might decide that you want them to be inspired to take up MA as an ongoing hobby, to learn something about MA history, to appreciate the tactical correlations between a set of techniques, etc.
Next is, obviously, to communicate thoroughly with the organizers well before the event, to make sure that you're both on the same page re. the logistics. It's common for non-MAists to under-estimate the amount of open space required for safe training, etc.
Presumably you won't have mats, which will generally count out any throwing or grappling work, especially with a large group of novices in a "taster" format.
In terms of instructing large groups; I'm not clear on whether your classes will be electives or whether the groups are simply cycling through several seminars in different subjects. Especially in the latter case, it's important to immediately get them used to the idea that you are in charge. As Sea Cadets your students will probably be better disciplined than average for their age, but it's always easiest for people to get into a receptive and productive frame of mind as students if the instructor is clearly in charge from the outset. Exactly how you do that depends on your personal style, but it is more important with large, unfamiliar groups than otherwise.
From your description it sounds like you want the seminar to have a self defense focus. There are plenty of situational awareness drills that can be done with large groups and without the risk of accidental injuries through newbie teenagers getting carried away in contact drills. As a general safety tip for this sort of seminar, if you establish s-l-o-w m-o-t-i-o-n as the default speed in your demos and drills, that will reduce a lot of risk. It also allows them to safely make actual contact.
Finally, mixing up the format frequently; partner work, small group work, whole group work, etc. - keeps things fresh.
It looks like there will be a total of 100 cadets attending Flagship. I will be available to those units which are interested (so, <100 total over the course of the event) for one hour instructional periods over the course of a single day. It is. . . Pretty bad, but I'm going to have to work with what I have; I've asked the CO to let the units double up so I'll have them for two hours at a time. Is there anything else you guys think I should ask for in terms of scheduling?
I figure it'd also be worth seeing if he can ask the coasties running the base gym if they can get some mats or pads or other equipment to work with. . .
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