Maria,
If he likes fish, there are two suggestions within the Magic Kingdom. First, there is the Columbia Harbor House, which is a counter service restaurant with a few fish choices, like a tuna sandwich, fried fish or fried shrimp, and New England Clam Chowder. There is also the Tomorrowland Terrace Noodle station that has many Asian choices, but it is only open seasonally.
As for the best "guy" things to do, I would hit the thrill rides in Frontierland that he might be interested in (Slash Mountain and Big Thunder Mountain Railroad), or possibly Pirates of the Caribbean.
Another idea, that may make it special for him, is the
Pirate's League. In that, he can get a pirate makeover. Not sure if that is too kiddie for a 10-year old, but I know of a few Moms Panel members who had it done to them. They are just a few years older than 10, and they loved it!
Write me back with more of what he likes, and I can come up with some more specific suggestions. Also let me know if he will have time to go to another park for other possible options!
Have a magical vacation!