Just to update all - I got it to work using the custom fields. So now people can register up to 5 children all at once for different groups. I really like the feature that allows me to put the user into a Joomla group based on their radio button selection, so I can still segment by group sign-up. Thanks!
Thanks for the update. I will try to find a solution for this requirement later as I know it is a valid requirement. Right now, there are still other improvements (which can be used by more customers) which I want to work on first
