My macbook air was restored by accident? maybe from my kids.... how do I undo this to get my movies and games and settings back?

If your disk has been overwritten but not wiped, it may be possible to recover some or most of your files. If your disc was badly fragmented, that will reduce the # of recoverable files. If you had an external drive for it, Time Machine should have backed up your hard drive, and can restore your MBAir; depending on the preferences setting, it may not have kept your games.
If you have an external drive, reconnect it, open Time Machine (double-click the counter-clockwise arrow towards the right end of the menu bar at the top of your desktop). Once Time Machine is running, check your timeline for a restore point.

Barring the above, a "third party application," I like Norton's Utilities, may be able to recover files or parts of them. Most likely you're better off reinstalling the item from its' original source. Good luck to you.