5D mkII AI or one shot?

Hi, hope this is posted in the right place, ive just started using my 5D mkII and 70-200 f4 IS to take shots of my kids, now which should I be using for the times the kids are running towards me? AI or One Shot? This is about the first time ive ventured into shooting people, I was primarily shooting landscapes and Urban scenes before, any advice greatly received thanks.

AI servo, it will track the child and refocus as they get nearer. If you use one shot, the camera will focus on one point and lock it, so when you take the shot the focus will be where the child WAS, not where they ARE.

One shot works great for landscape and urban scenes as they don't run around.

Yep as above, just dont use AI Focus, that just attempts to detect if the person is moving or not and switches between AI servo and one shot. its not very accurate and mostly gets it wrong, stick to AI Servo and one shot.

Thanks to both of you, I took some shots, found AI servo shots came out nice and clean/sharp, after years of landscaping I need to practice more, thanks again.

AI SERVO

If you select one point you need to keep that one point on the subject, or the camera will not track.

If you select all points, you NEED to start tracking with the MIDDLE point, no matter what, the camera will start tracking with the middle point, but after that, the camera passes the info to the other points. So, as said, start tracking with the middle point.

Also AF Point Expansion (Custom Funcion) helps. It activates 6 additional (hidden) AF points around the middle point, that help tracking a lot.