I have no problem with younger kids taking the class. IMO, 10 or 11 is the youngest that should be included in an adult class. And yes, it is better if the parents are also taking the class, but I also think that it should be mandatory for the parents to stay with the kids while the class (both classroom and pool) is going on. One, because it is not a baby sitting sessions and two, because they will be able to see if the kid is capable of diving or if they even have an interest.
Let's face it, safety is the bottom line. If this is accomplished, the fun follows automatically.