Raiser's Edge lets you set a default "maximum number of members" on a membership category, but there's no way to set a default number of children for a membership category. Now that we are using REConsole to connect Raiser's Edge with our Galaxy POS system, this is a real problem for us.
We have the same issue and have added new idea RE7-I-3823 as we didn't realize someone else had already raised it.