AI focus starts in "one shot" mode (ie you get focus lock indicator), but then converts to AI servo once movement is detected. AI servo is never in "One shot" mode, so your focus lock light won't come on - it's constantly looking for movement. Most importantly, AF servo will shoot even when focus isn't locked, so you do get more out of focus shots.
I'd shoot in one shot or AI focus for that sort of subject. Your subjects are fairly stationary (as compared with birds in flight say, and even in that instance one shot works really well).