These are all great comments, and I appreciate the feedback. Thank you everyone!
At a minimum, I think it's worth my calling the conservatory for sizing recommendations to see if there are good quality instruments available in his size and receive cost estimates. He already takes weekly group music classes, so his teacher can put me in touch with be early childhood staff.
From brief Internet research, some decent manufacturers scale classical guitars down to 1/8 size, and Fenders scale to 1/4. I don't have deep knowledge around guitars, so I'm going to consult a teacher at the conservatory to discuss brand quality. DS specifically asked to learn electric guitar, because he "wants to learn to play the Beatles' music", which mitigates the acoustic quality issue. When I checked sizing guides, he is on the low end of the recommended height range for 1/4 guitars, which are typically sized for 4-6 year olds. He has big hands, wears shoes sized for 5-year-olds, and is above the 90%ile for height for age, so I'm fairly confident putting outer bounds on starting guitar at 4 based on sizing considerations.
If we hold off on guitar until next year or the year after, I love Dude's suggestion about drums! You know my boy well, Dude; he thinks Dave Grohl is amazing.
Mana, I specifically had you in mind with this thread. If you're comfortable, I'd love to hear more about your DD's experience with her classes, either on the thread or by PM. I think there is a strong case to be made on both sides, and it largely comes down to matching the right child with the right teacher when the child can reasonably physically handle the instrument.
