Despite our talk about what works "best" the good folk at Cameraland are doing an admirable job keeping things in perspective.
So I thought about it a bit and came up with this suggestion;
Try shooting your 60D and existing lens at high ISO's to see what you get.
Then rent a couple of lenses from these online rental services. Rent one that you're considering buying and see if it makes the difference you had hoped for. Also rent a lens with a 2.8 aperture and see if the fuss is all that.
Good luck and I hope you capture your son's senior season in good fashion!
