Originally posted by amp Any thoughts/opinions would be appreciated.
Since the subject is going to be kids, another option would be a camera with very good face detection AF. I'd look into something like a Sony A5100/A6000 with just the Sony SEL 18-55 f3.5-5.6 kit lens, which is quite decent. The face detection autofocus of NEX/Alpha works great.
Alternatively, just start shooting your K-3 in live view with face detection turned on when kids are around. The K-3 face detection in live view works too, albeit not as well as it does in Sony mirrorless.