In most chess games between reasonably strong players, the game ends by a resignation or ends in a draw. It's very rare, at high levels, for it to go all the way to checkmate. For examples, see http://www.anand-topalov.com/
That is the website for the most recent World Championship. 2 million euros in prize money, 60% to the winner, 40% to the loser. The winner has other benefits, also, so this is clearly serious chess. Every game that was not drawn ended with a resignation. I suspect that every game that ended in a draw was drawn by mutual agreement.
The nature of the beast is that before checkmate occurs, both players can see that checkmate is inevitable, so the losing player simply resigns instead of playing it out.
You might consider having one player resign a few moves before the mate, and having someone who is watching ask "Why did he resign", to show how the mate would play out if the game had continued.
It sounds like you need to find a local chess player to help you out with your project.
If you want to use the knight in an interesting and realistic checkmate where the knight gives the mate, perhaps look into smothered mates.
http://en.wikipedia.org/wiki/Smothered_mate