Probably not a problem.
Here are the relevant questions you should be asking:
1. Are you ok with the person he is if he is not taking it? If not, what are the chances he will need to stop taking it.
Since it is a boy, you don’t have to worry about effects in pregnancy (which even for a girl are not very concerning in this case, by the way), so it is unlikely he’d ever need to stop taking it. But to make yourself satisfied, you could ask him to not take it on dates after a couple of dates.
2. Are there long term health effects?
So this drug has been around for a very long time, and there really are not long term health effects. So you can feel pretty good on that score also.