I think its too early because of his physical immaturity and the fact that he is just a Freshman (although he is big and strong, he has just recently stopped talking like minnie mouse i.e. voice change).
I had to comment because the Minnie Mouse reference is funny and created quite the mental image.
I was torn about this with our 2018 as well. In your favor is his size. 6'4" at 14-15 is going to garner some attention. Mine is "only" 6' so you have an edge there. We did do one college camp and a local prospect camp (both relatively inexpensive) over the winter of freshman year and summer after freshman year. My thought was that it was good practice and it helped him learn about the format and expectations of these events. I was not expecting him to garner big attention. However, we opted not to attend the recent PG showcase in our area because I didn't feel like he was ready for that level. The advice I received early on is to showcase once you have something to show. I don't think my 2018 is quite there yet. Our goal is to be in that place by next summer (between SO and JR years).
I know there are a couple 2018 parents on this site with kids in your son's size and velocity range. They opted to start showcasing this past summer (after their Freshman year) and it seems to be paying off.
Good luck!