I would do what you said...Start little by little. I'm not an expert, but to me if you start out with heavy weights you pull your whole body down, basicly, trying to pull that one weight up. You stunt your growth a bit, depends on how often the person lifts. Since he is 12, he should start out with a 10 lbs weight, then up to 15 or so. Depends on his current strength. Another alternation is push ups. They are great for muscles expecially for his age.

Young childeren can injure their growth plates if they lift heavy weights. Tell your freiend to talk with her sons md befor starting the exercise!

Talk to the docter if you feel uncomfortable. I would say its ok, however start slowly. Learn the porper lifting techniques and jsut do light or body weight movements.

He should start with low weights & when these can be done easily 10-15 times each then move up a level, so long also as a) his muscles & joints don't hurt & b) he's also eating extra because the more exercise you do the more calories you burn so the more food you need - I am assuming that he's not overweight.