I wouldn't. I remember once when I was ~10 I met a young adult that stuttered, she was about 20. She noticed my stutter and tried to be a 'friend' about it but I immediately felt embarrassed and shut down even though she was very nice. Kids largely don't have the maturity to acknowledge their shortcomings and face it positively if you put them on the spot. However if the kid brings it up, I think it's fair play.