iPhoto duplicate and triplicates...???

Easy, if you had the teeny bit of foresight to use TimeMachine, which is free and merely requires a $50 disk to backup to, you could just go back in time to a point before your kids played around with it and messed it up.

Or, if you had the foresight to take say weekly backups, you could restore the most recent good backup.

Assuming you didn't bother to take backups or use TM (why ask ask here otherwise?) , then you'll have to give the kids their own logon, forbidding them from using yours, manually go through your photos deleting photos you don't want and then switching on Time Machine. The reason you'll have to go through manually is because up to and including iPhoto version 11, there is no magic "put the photos into the way I want them" button.

No apologies for the rudeness, it doesn't take rocket science to imagine that a computer might go wrong and that you should take precautions against that.

Consider the time you spend fixing up your iPhoto arrangements, a cheap lesson in why backups are a good idea, and why kids shouldn't be allowed to mess with stuff you care about. You got off lightly, you might be asking which of several companies you should be spending $1000 with to recover all your photos from a busted disk.