I would be reluctant to get him some weights ,,,,unless you know what your doing,,,,
Get him to a gym,,,and get some guidance,,,as far as 14 goes it's no problem, but he needs to learn properly to lift a weight ect ect,,,
Is he not interested in other sports,,,boxing martial arts ,,football ,,rugby?
yeah il be honest i think a gym is the way to go as im clueless about the subject,start him off right i reckon cheers