Walt, I usually shoot AV mode as well but for a beginner it's more important to keep the shutter up then have the aperture locked down IMHO. You obviously know how to use the ISO to keep the shutter up where it needs to be.
Randy, the reason I asked about your picture styles is it appears your shots could use a tad more sharpening either in cam or in your editor. Also that sports mode you're using is giving you faster shutter speeds then a regular metering mode but in your first 2 shots it's barely fast enough and in the shot of Chris as Walt pointed out ISO400 wasn't really needed. Although it's better (again IMO) to have a slightly faster shutter (1/1600th in this case) then not enough because ISO400 is perfectly clean on the 40D. In your first two shots f4 at ISO400 would have given you more shutter which might have helped because I'm seeing a bit of motion blur in one of those. (BTW did you get a 70-200L? if not I suppose f4 might be out the window! :-) ) That metering mode you're using appears to be locking the cam at ISO 400 and then balancing the shutter (biased towards a faster speed) and aperture. that's still leaving too much to chance.
Another thing you can't discount if you're new to all this is camera shake which is not impossible to get zoomed to 200mm or longer at anything under 1/1000th. Heck with my 400 f5.6L I can get it occasionally up to 1 / 1600th.
I wish I had the original file you took of Chris I tried tweaking yours a bit below with marginal results because one can't do much with a fully compressed jpeg.
You're right there, with just a little more control over your settings and post processing I think you'll start amazing yourself. I'm going to try and get up to Shasta in Aug when the Twelkers are there, maybe we could hook up then?