It's not all MegaPixels fwiw, but that's what marketing is all about ... (eg, you need 5MP to get 8x10 prints). Focal length has no bearing on shutter lag (perhaps other than focusing). Shutter lag is usually due to 2 components - when you press the shutter button, it takes x amount of time for the camer to bring the subject into focus - every non-dSLR suffers from this problem. The second component is the amount of time the camera takes to execute the rest of the "photo taking" - getting the exposure, operating the shutter, etc - this is around 1/10 of a second for most good P&S cameras. fwiw, all the cameras you mentioned suffer from slow auto focus, even the prosumer models (up to Canon Pro-1 for eg). The ones you mentioned arent' good in low light situations either. The only P&S that is good in low-light is the Fuji F-10; not sure about responsiveness though (I'm sure users will chime in).
Now, this is all assuming you want to take indoor/low-light shots of kids while NOT using a flash - it looks like your only option would be a dSLR, esp. Canon.
All of this being said, technique plays a much greater part imo. If you are very familiar with your camera, and you learn to anticipate what you're shooting, imo you can get great results from what you're intending to shoot with any good digicam, not just a dSLR.