Sports in general means stopping the action. Kids are slower than pro athletes, but you still need a good range in shutter speed.
With that in mind, IS/VR is no use because both technologies prevent camera shake at slower shutter speeds, and obviously slower shutter speeds does the exact opposite of stopping the action. However, IS/VR is nice for low-light, handheld use for other purposes, so if you plan on using your lenses for more than sports, you may wish to consider getting IS.
So, what do you need in a good sports photography lens? Lenses with wider apertures (aka faster lenses) give you more light to work with, allowing faster shutter speeds. In addition, the faster the lens, the better your camera's AF will perform. On most prosumer bodies, the AF points require at least F2.8 to achieve their best performance.
Focal length's will depend on how close you can get to your subject, as well as how much cropping you can get with your body. If money is no object, then a 300, 400, or 500mm prime will do you well, but they're really expensive, so a zoom around 300mm might be a good start, or even a good 70-200 with a TC in a pinch (though the latter option does reduce your working f-stop).