you can disable some features in the config..here's a link .Toolbar
I wanted to build a demo for clients also...the way I did it was build a dummy page with no links back to the original site...a hidden standalone page that you have to enter the address manually to view...then I applied cms to that page and let them use it as a "cms training page"..no one will see it so thet can mess around all they want and post updates.
I throw one of these pages into the clients site....not mine