Just a Nikon heathen here, but I'm looking at this thing right now, which also comes in Canon fit:
First Look: Tokina 11-16/f2.8 AT-X Pro DX
It's either that (fast-ish at f/2.8, if not up to gizze's specs) or the Sigma mentioned above, which goes to 10mm but only f/3.5.
There may a Canon-only doobry that I don't know about, of course.
I'd second the charm of a 50mm f/1.8 for the sprog-recording purposes you have in mind, though being a Niko-Mug I pay more for the same lenses (according to the guys here) - £85 for me ...):
