Indoor dog shows?

I need a lens for my daughter's indoor dog shows.  I'm shooting with a crop sensor (Canon 60D).

Criteria:

1) poor lighting

2) girl & dog in motion

3) usually shooting 30-60 feet away

4) flash not allowed

I own a 60D with legacy glass, so everything has been manual focus. I'm interested in others' experiences in similar conditions, but with newer lenses.  (An 85mm 1.8 is tempting.)  Speed and accuracy of focus are huge.

Any thoughts?