Rugby Union, Surfers Paradise

A friend plays in the Surfers Paradise rugby union second grade side and I recently went down to the field for a look. Lighting ranged from overcast to patchy sunlight so I figured b&w conversion on all images might be the trick. Its certainly harder than it looks trying to anticipate the plays and then focus on one or two players.
Shot using a Sigma 70-300DG at ISOs up to 800 and around f8.
<a href="http://www.flickr.com/photos/jonasphoto/209481396/" title="Photo Sharing"><img src="http://static.flickr.com/68/209481396_ea54f361cc.jpg" width="500" height="333" border="0" alt="John, fend off" /></a>
<a href="http://www.flickr.com/photos/jonasphoto/209487744/" title="Photo Sharing"><img src="http://static.flickr.com/96/209487744_cb6468027b.jpg" width="500" height="333" border="0" alt="John, tackle" /></a>
<a href="http://www.flickr.com/photos/jonasphoto/208889301/" title="Photo Sharing"><img src="http://static.flickr.com/91/208889301_3a1fdf7651.jpg" width="500" height="333" border="0" alt="Surfers Paradise second grade" /></a>
<a href="http://www.flickr.com/photos/jonasphoto/209487747/" title="Photo Sharing"><img src="http://static.flickr.com/80/209487747_e76a5e9225.jpg" width="333" height="500" border="0" alt="Line out silhouette" /></a>
Any suggestions on which is the best focusing setting to use? I am atill unsure if AF-C is quick enough. What about the other settings? Dynamic, closest object etc?
Shot using a Sigma 70-300DG at ISOs up to 800 and around f8.
<a href="http://www.flickr.com/photos/jonasphoto/209481396/" title="Photo Sharing"><img src="http://static.flickr.com/68/209481396_ea54f361cc.jpg" width="500" height="333" border="0" alt="John, fend off" /></a>
<a href="http://www.flickr.com/photos/jonasphoto/209487744/" title="Photo Sharing"><img src="http://static.flickr.com/96/209487744_cb6468027b.jpg" width="500" height="333" border="0" alt="John, tackle" /></a>
<a href="http://www.flickr.com/photos/jonasphoto/208889301/" title="Photo Sharing"><img src="http://static.flickr.com/91/208889301_3a1fdf7651.jpg" width="500" height="333" border="0" alt="Surfers Paradise second grade" /></a>
<a href="http://www.flickr.com/photos/jonasphoto/209487747/" title="Photo Sharing"><img src="http://static.flickr.com/80/209487747_e76a5e9225.jpg" width="333" height="500" border="0" alt="Line out silhouette" /></a>
Any suggestions on which is the best focusing setting to use? I am atill unsure if AF-C is quick enough. What about the other settings? Dynamic, closest object etc?