This is an important topic, kudos for taking it on. It's not clear to me though whether your inteneded audience is kids or parents. If you are going to be instructing children in the safety basics, CD covered those pretty well. There are chapters more that you'd want to include if the seminar is for parents.
I just have a few additional comments:
1) Tethers --which have been recommended by some -- are a good idea in some circumstances. However, just like on land, they can pose a serious strangulation hazard for very young children (infants/toddlers).
2) PFDs -- Like Cruising Dad, we found the Mustang Li'l Legends to be the best design for comfort/safety. Personally, I would not use an inflatable PFD for youngsters. Too many working parts and the risk of malfunction. Failsafe closed cell foam is preferable.
3) When to wear PFDs? Most parents realize that the kids need them when on the boat. But some forget that the dock can be even more dangerous. Teach the kids to put them on when they arrive at the marina -- and keep them on at all times unless they're safe below in the cabin. Also, don't forget to wear the PFDs when out in the dinghy. These are good general rules, especially for non-swimmers. As kids get older and more responsible, parents can modify the rules based on the situation and swimming ability.
4) Safe Place: Several others responded about the importance of a secure/safe place kids can go when parents are busy managing the boat or conditions are becoming challenging. Jotun even suggested a porta-crib. Our boat is fitted with an extra-tall, athwartship lee-cloth at the aft end of the v-berth, which closes it off entirely. This worked well for us when our kids were tots.
Here's my gang playing on the bowsprit a few years back (Mustang didn't have the infant/toddler size PFD back then, but now they do)...