It's like that cute 11 year old singer on 'So you think you got talent'(can't remember her name) that was told by the one moron judge that she sang good but had to 'change your hair, change your clothes, change your shoes).
Next thing you know, instead of looking like an innocent kid, she looks like a small 'adult'.
Totally bull.
Let kids be kids.
The most memorable kid performers to me are the ones in commercials that look and act like KIDS. Some kids have talent. They don't have to be "little adults" to express it. Like you said, let 'em be kids.