Your son has a strong profile. On top of that, however, he has to make an interesting story and show passion for the ED school. Now matter how knowledgeable, people on this board will NOT be the person to tell you which school would be the best fit for your son. He will need to decide that for himself.
If I were in your shoes, I’d have him look into courses/programs from each of school, and make an honest evaluation of what he likes and dislikes about them. Then learn to tell his honest story in an engaging and heartfelt manner in the essays/interviews. Be genuine and honest. Interviewers (I have been doing it for 20+ years) can tell if a candidate is being truthful in a heartbeat.
If your son would be equally happy with any of the schools, then playing the legacy card and ED with Penn might be the best bet. If he prefers Harvard or Yale for a valid reason, then he should ED there, and you should be supportive.
Good luck!