I don't think there is any educational content that you can create that has not already been created by the United States Power Squadrons, now called, as already noted, America's Boating Club. From introduction to boating classes, to celestial navigation, marine electronics to anchoring, trailer boating and knot/bends and hitches seminars, you can't beat the USPS educational offerings. There is even an online training option.
I don't want to discourage you from your venture, but you'll need to get very specific to avoid duplicating what's already been done. Maybe a better use of your resources would be to join a local power squadron or USCG Aux, unit and volunteer to do Vessel Safety Checks at your local marinas and boat launching ramps. That would do more to improve boater safety than any kind of webinar.