night HS football playoff advice requested

In few hours at small college stadium.
Am stock photographer so some action experience.
Not shooting for news but for my own stock -- no pressure.
Shooting more sideline & crowd color, but also want tight generic game action.
Limited to Canon 100mm f2.8 on Canon 7D (=160mm?)
Stadium lighting + fill flash probably = 1/160sec @f2.8 ISO 800.
Have sideline-endzone access.

Am guessing if I'm always 10 yards downfield from hike, about one in four plays will fill my frame at some point...?
Is 1/160sec fast enough? Should I go ISO 1600? Too much noise?
Any advice appreciated.
--
regards jg
http://www.PhotosPhotos.net