Showing and Hiding Sidebars Efficiently

Hi,
I am trying to set-up my website with certain content only for registered users.

(www.thebirdschool.com)

Right now I have two menus at the top and an inner and outer right sidebar.

I would like to set-up a category: www.thebirdschool.com/registered-members

for these, I would want to hide the inner and outer right sidebar and show a left sidebar instead

It seems extremely cumbersome to have to type in all categories and pages from which to hide those sidebars from. There are a lot of them. Is there an easier way of doing it? or am I better off to setting-up a new website for this?