I don't think this is chess related,but blowerd(no offense,) do you think black would really do Kf8 and Ke8 over and over again?But the get the knight to pawn is correct.
Also, I suggest that for 8year olds, you shouldn't do blitz or bullet because they are going to play random moves to stay on time and then when there playing standard they may play random moves. Give them enough time to think.
Gambling is an important skill to learn - when the probability is on your side or not. In this case, I'd say that given enough time, the kid will beat you.
Gambling.It is a skill, but not a important one. You do it like only in casinos, winning prizes with dices, or poker. But it is CHANCE. Chess is SKILL. Not chance.
(I still say you're encouraging gambling...)
Ummm.... that is to motivate them to practice more and win.
Possibly helpful:
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
https://www.newinchess.com/Shop/Images/Pdfs/7192.pdf
Logical Chess: Move by Move by Irving Chernev (1957)
https://web.archive.org/web/20140708104437/http://www.chesscafe.com/text/logichess.pdf
The Most Instructive Games of Chess Ever Played by Irving Chernev (1965)
https://chessbookreviews.wordpress.com/tag/most-instructive-games-of-chess-ever-played/
Winning Chess by Irving Chernev and Fred Reinfeld (1949)
https://web.archive.org/web/20140708093415/http://www.chesscafe.com/text/review919.pdf
Discovering Chess Openings by GM John Emms (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
Openings for Amateurs by Pete Tamburro (2014)
http://kenilworthian.blogspot.com/2014/05/review-of-pete-tamburros-openings-for.html
Chess Endgames for Kids by Karsten Müller (2015)
https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
http://www.gambitbooks.com/pdfs/Chess_Endgames_for_Kids.pdf
A Guide to Chess Improvement by Dan Heisman (2010)
https://web.archive.org/web/20140708105628/http://www.chesscafe.com/text/review781.pdf
Look, teaching children chess is much easier than anyone thinks. I learnt it when I was nine and for the next three years I slacked off and generally left my chess set to accumulate dust. A couple of weeks ago, I picked it up again and discovered that I could still play pretty well.
Personally, I think that what would motivate him would be an association with protecting en prise squares and rewards(also known as positive reinforcement, but that sounds too much like psychobabble).
What you do is, you threaten an en prise square, and if he protects it, you attack it anyway, and make convincing(very convincing; we know when you're faking it) gestures of surprise. If he doesn't protect it, attack it and he will be like,"Aww man" and note the mistake to correct it next time. Repeat until he gets it.
Have you also taught him about castling and more importantly, when not to castle?