Hi there,
It is always great to hear of the children getting involved as it is something that they can do their whole life. Families that do this together really have some great adventure possibilities.
When it come to teaching children, and I teach for two agencies the requirements are the same for the children as the adults if they go the Jr. Scuba / Open Water Diver. That said the ratios are indeed stricter as children do take more attention. With children I never have more than two unless there is another dive professional there and only two in the water at any one time with me. Smaller classes I find help people get into the comfort zone needed to be great divers and if they learn that early the rest seems to fall into place much more easily for the student and surely for me.
My local dive club has a few Jr. Divers in there and they are great in the water.
Take care and Best Fishes!! `•.¸¸.•´¯`•.¸>