I (and my wife) were shooting at GSR mostly from the stands, as I was the drive coach and couldn't get down closer much. I found that I had to push it all the way to ISO 1600 often. I was using the Tamron 28-300 VC which is a great lens, but f/3.5-6.3 so was still a bit slow at ISO 1600 in a lot of cases. Still, better to get the shot than miss it.
For a shorter lens, I highly, highly recommend the Tamron 17-50 f/2.8. I've used it for 18mths now and it is almost permanently attached to my camera. Only when I know for sure I need more reach do I use the 28-300. But the quality of the glass in the 17-50 with the constant f/2.8 gives stunning images.
My Canon 50mm f/1.8 is also great for team member photos etc. One of the sharpest images out there, and the best $130 (Australian) I ever spent for my camera!

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FRC Team 111 - WildStang (Mentor, Drive Coach)
FTC Team 7458 - Full Force! (Mentor, Coach)
FRC Team 3132 - Australia's FIRST FRC Team! (Holy crazy first year, Batman!)