Building Endurance and Speed
Terry has recently posted per the four competitive strokes on the TI web since he was focused on breaking the Adirondack Masters records in a number of events during nationals, so check the past forum / blog inputs.
Also, the book Long Strokes in a Short Season by Art Aungst a Total Immersion Coach is available on the TI site. I have read it, even though I don't coach children or the four strokes and found it very informative and helpful per my own swimming.
Hope this gives you a couple of quick starting points.