Out of focus on my shots

My sister in law just got married last week and I took a few shots of the event. I was taking a picture of the entourage and I employed the focus and recompose (technique). Then after I took them I checked my shots and a lot of them are out of focus. Then I realized I'm on One Shot AF Mode which made me conclude that when I focused on their eyes while they are walking, and then recompose, my focus is left behind from where I half-pressed (focus) the shutter, so that when I pressed the shutter completely and took the photo, it will be out of focus indeed?

Is my assessment of my fault correct? Do you think I should have used AI Servo instead? Please confirm this.

That sounds about right. If they are moving towards you or away from you then the focus & recompose method won't work. You need to change the af point to the nearest one to their eyes and use ai servo to track them as they walk.

Thanks Mike. Very helpful.