I am not a HS coach, but I have no problem with your son trying out as a position player and pitcher. A team could always use quality pitchers. First of all, if it helps him make the team, he will still have time to prove himself as a position player as well. What ever event my son is going to, he always lists himself as a RHP, middle infielder. Especially as a freshman, it is not time to decide on one or the other. Let him try out as both and let the chips fall where they may.
Last year, my son was a freshman. Tried out as pitcher and where ever else the team needed him basically. He wound up pitching varsity and playing position on JV. This year, he is on varsity as a pitcher and position player. He grew up playing mostly short and second. Played a little third and outfield. Well, this year on varsity, the SS is a junior who has already commited to Clemson and the 2nd baseman is a senior who wants to play 2nd. In the two games and one scrimmage we have played, he has pitched in two of them and played 3rd, right field and DH'd. The more versatile you are, the better your chances. I would have him let the coach know he plays first as well. You just never know.