Forget about throwing the curveball when you are 9 years olds. Here are three pitches that a Little League pitcher can use to keep hitters off balance and mess up their timing.
1) 4-seam fastball
2) 2-seam fastball
These pitches can be thrown with the same arm angle and speed. The key is to locate the pitches on the corners or low in the zone for strikes.
4-seam Fastball - The Heater
Use the 4-seam fastball on most of your pitches. Throw the fastball on the inside or outside corner for strikes. If they start fouling it off, then switch to the two seam fastball.
2-seamer - The Sinker
Hitters have trouble tracking the movement of a 2-seam fastball, especially when thrown by a lefty pitcher. The 2-seamer thrown toward the middle of the plate, by a lefty, can run low and away from a right handed hitter. The pitch will run to the outside of a left-handed hitter, when thrown by a right-handed pitcher.
Cy Young award winner Félix Hernández throws a fastball that has been clocked at 100 mph, although he does not rely entirely on overpowering velocity. Instead he uses a two-seam fastball, which comes in a bit slower but with more movement and the ball sinks as it approaches the batter. (Wikipedia)
The changeup - Keeping the hitter off balance
The chageup works great for keeping a hitter guessing and makes them look silly when they lunge at the slow moving ball. The pitch is thrown with the same arm motion as the fastball, but using a loose three finger grip.