Multiple child themes from 2011 theme

Multiple child themes from 2011 theme

1. If I want multiple child themes would I place each one below the other? Example:

2011

2011 index.html

2011 classifieds

2011 Yellow pages

2. Or would I put them into a child theme folder? Example:

2011

Child theme <<Folder and place all the child themes in it.

3. Or should I just copy all the files from 2011 and make all new complete themes and just update the files manually with each update release?