Sliders and 12 y.o.

This question is a practical what should I do? problerm along the Bob Feller/curveball query. We're getting ready for all-stars, and my job is to prepare the pitchers. IMHO most of the coaches in our league are delighted with any kind of strike, so the level of training in mechanics and pitch selection is primitive.

I generally teach a tall-and-fall approach with the 4-seam fastball, concentrating on balance position, direction (head and ball of foot moving toward target), extension, and followthrough (with arm ending up below and outside the knee). After several sessions, we move on to grips, with the 2-seam, split-finger, circle change, and LL change grips. Of course, no one can throw all those pitches, but you usually can or can't get the hang of a pitch in short order; then you select the two or three that work best. (I particularly like the circle change for left-handers, but that's another matter).

Tonight, I went over a two-seam cut fastball delivery with one of the hardest throwing kids in the league. After going over slow mechanics from a short distancee, I had him use the grip and throw me a couple long tosses.

I nearly dropped my drawers when I saw a perfectly formed white dot come in surrounded by a red circle.

I dropped down into catching position and, sure enough, the pitch moved like a tight slider, with excellent down-and-away action. The speed was slightly slower than I expected (a little slower than a regular two-seamer), but it still had plenty of fire, lots of movement, and he kept throwing the pitch in the strike zone (5 of 6 tries). I'm know the kid has been throwing a variety of the curve with mixed results, but I was astonished to see a full-blown slider.

Practical question is what to do. Should I shut that pitch down? Talk to his father about the various opinions on breaking balls? Rejoice in this good fortune?

Help me out, guys -- what would you do???