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[Mark L]

Focusing: set the camera to AF-On button focusing only. That is don't let the camera focus with a half press. I see you have a 5D. I'm pretty sure you can set this up in camera. Only focus with your thumb. if it feels a bit goofy at first, this can be normal, but most folks that have switched won't go back to the half press method.

I find this true.
I like using the back button focusing (BBF). Personally I think it should be the default settings in cameras. Very easy to use.
The Canon manuals don't make it that easy to find how to change to it. So google or look at this (though I have a few issues with what she is saying, though what she says about focus lock is good for things that aren't moving much. Weddings?) to see why and how to change you cameras settings .... https://www.youtube.com/watch?v=B0c9PrYZe14

With kids moving around, try keeping your thumb on the BBF and use AI Servo as you focusing mode.