Here are some other things to consider:
Will he have a realistic opportunity for PT playing up?
Will this interfere with his rec or travel team schedule and is he, his coaches, and you comfortable with any possible repercussions?
If he is a pitcher, do you know the coaches involved and that they will respect his arm? (And is your son mature enough to recognize that he will be facing larger, more ‘dangerous’ hitters?)
My son played up as well, and thrived. The elevated game meant that plays that wouldn’t have been a possibility with his other teams were completed, that he could face superior pitching and gauge his progress against it, and that he had to anticipate that same level from the opposition. He also learned very quickly how to position himself to deal with getting trucked at the plate by guys, literally, twice his size.
On the whole, I would recommend it. But a discussion with your son in advance about all the points advised here will help prepare him, as well as give him an opportunity to tell you his expectations and concerns.