well for the children that depends on weather you mean on witch god should or could have children or abilities for their children. Ever way Poseidons kid could have the ability to breath underwater as well as use it to heal himself and others like percy jackson from the film but the power to control the water like he dose would be a bit much for this type of RP. However he could still generate ice and shout out a small ice beam or something. Hades kid could have the ability to create and throw fire balls or even breath Fire at most as that would be about as strong as the power to cast small spells. As far as the plot goes nothing springs to mind at the moment.