I told my wife that I would never love our children enough to let them get a drum set.
I think the band director gave you some solid advice. In addition to providing a solid foundation for musicality and learning other instruments, I think piano is the most pleasant classical instrument to listen to when played without accompaniment, particularly when the musician isn't yet skilled. Violins take up very little space, are portable, and much cheaper than pianos (for equivalent instrument quality).
Unless you are planning on your child's instrument mastery being the hook that gets them into their preferred school and can accurately predict which instrument will be in demand on the marching band ten years from now, I wouldn't bother trying to micromanage their choice of instrument(s) beyond the introductory piano or violin choice.
