If he goes to Florida Tech, he can easily switch from AE to ME (or any other E) if once he gets into it he feels there aren’t enough opportunities in AE. The only engineering he might fall behind in is chemical engineering just because ChemE’s take 17-19 credits per semester while the other majors can get by with 16-17. Even that isn’t really an issue as there are online classes which can be taken to catch up.
Flor Tech has a general engineering course the first semester for those who are unclear which way to go. My daughter took that and decided on civil, which surprised me as she was thinking ocean or chemical. My nephew also switched after a semester from something (I think EE) to ME. Those first few semesters are very similar for all disciplines. Except chemical.
I really think after he talks to professors and other students, or maybe even employers after a year, he’ll know which path is right for him.