Metro setup for small children's computer

I'm trying to set up the Metro UI for a small children's computer a a local public library.  Each game has it's own icon and ideally, the children could run the game, close the game and the computer would return to the Metro UI for a consistent, locked down, experience.  The kiosk kit would be great, but there are 10-12 games and more to come.

Currently, the desktop sometimes opens when the game closes.  How do I start to lock this down?  Do I need to look at vitalization?

Brett Upton