Right, the 100-400 is your lens and use the 30D. It should have enough reach considering the crop factor on a 30D gives the equivalent of over 600mm. I use Nikon so I can't say whether the AF will handle the situation or not. It's probably better to manually pre-focus on the spot you want to take the picture.

I've never actually watched from Ballacrye to be honest but quick as it is, you'll need a fast shutter speed both to handle the speed of the subject and to reduce the risk of camera shake if hand holding.

I'd try and get somewhere you can move from because there's only really one shot at Ballacrye and while a few really nailed on shots of an airborne bike look great, it starts getting a bit tedious once you've taken 300!

A possible alternative is the drop down to Kate's from Keppel Gate. There are some big wheelies these days with the bike leaning over and you have the option of moving around for a variety of shots.