Depending on budget, get the 55-250, the 70-300, the 70-200 f/4, the 70-200 f/2.8, the 70-300 L, then perhaps the 70-200 IS versions.
Whe shooting moving subjects, shutter speed is more important than IS, so light (f/2.8 over 4 over 5.6) is most important.
If you can live without zoom, a 100 f/2.8 or 85 f/1.8 could be useful, but I think you need more focal length.
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