Library website - want multiple themes depending on area being viewed

I have set up drupal before, but only one theme for a single site. Now I would like to flex my know how.... and well.... I don't know how! ;)

I want to create a site for a public library. They serve people of all ages. For simplicity we want to focus on three groups - Adults, teens, kids. We would like to have each portion of the site to be theme specific to the age group. What is the best way to do that? I do not want to have three different installs or different databases, if I don't have to, but I fear I might.

If I'm at the library homepage, and click kids on the menu, I would like to go the to the main kids node (and sub-nodes) and then have a new theme from there. Click home, would like to go back to the home node and the default them. Click teens, go to the teen node (and subnodes) and have the teen theme.

Possible? I think it is but am unsure how to proceed. Any suggestions would be greatly appreciated!