MIkell,
A place called Ambergris Delight made some pretty awesome pizza. They deliver, and also have conch pizza. It was to die for. So that solves your seafood pizza question.
Breakfast in San Pedro isn't the normal continental or American breakfast. I suppose you could find scrambled eggs and toasted white bread, but they are known for their fry jacks, johnny cakes, seafood omelettes, breakfast burritos, fresh fruit, coconut tarts etc...... Burgers and fries are everywhere. No problem there. Don't worry. There will be plenty for him to pick from....