Zoo is depressing. Go Wild Animal Park! Go snorkeling! Go to the new Children’s Art Museum near the convention center! Take him to see the Midway aircraft carrier and all the jets/subs/ships you can tour over there then go for soft-serve at Seaport Village! I also like the pier fishing idea or you can go deep-sea fishing for about $60 per person including all gear, cruise, and licenses. You will see all kinds of great stuff out there. Or rent a jet ski! Those are super fun.
Better yet, print out this thread and let the boy choose! Let HIM teach YOU how to have fun!
Lastly, the wind has been great lately. Go fly a kite!