Welcome to the site. Unless he has been getting early attention from big D1 schools, it's a little early to be worrying too much about that. The benefits of showcases at this point would be to get comfortable with the format, get some unbiased verified measurables posted and hopefully get a look at a broader scope of good players so he has a better idea of what he will be competing against when the recruiting efforts become more serious. As he works on refining his skill set, it will become more evident what position/s he will want to showcase next year and the year after.
The experience and ability to play multiple positions will benefit him going forward. He has good height - this will also play in his favor as someone who is "projectible". Don't worry about the "young for his grade". He will either be a player or he won't. Colleges won't care about it much. They will just care about whether he is good enough to help them win. The concern would be more if he was particularly old for his grade. This would make it more likely that he has already physically matured and won't continue to grow and develop. Either way, no sense in worrying about controlling something you can't control. Make sure you don't get too far ahead of yourself - enjoy the HS years!
Also, be aware that you can search any topic on this site. You have found a tremendous resource at the right time!